Laminated body comprising porous layer and functional laminate using same

ABSTRACT

A layered body which includes a porous layer. The layered body having improved properties, such as adhesion between its substrate and its porous layer by the formation of a crosslinked structure; a functional laminate using the porous layer layered body; and a production processes thereof. The layered body includes a base and the porous layer on at least one surface of the base. The base is a resin film made of at least one resin material of polyimide resins, polyamideimide resins, polyamide resins, and polyetherimide resins, or is a metal foil piece, and the porous layer is made of a composition containing at least one polymer of polyimide resins, polyamideimide resins, polyamide resins, and polyetherimide resins as a main component, and a crosslinking agent. Additionally, the porous layer has fine pores having an average pore diameter of 0.01 to 10 μm, and a porosity of 30 to 85%.

TECHNICAL FIELD

The present invention relates to a layered body having, on its base, aporous layer made mainly of a polymer, a process for producing thelayered body, a functional laminate using the layered body having theporous layer, and a process for producing the laminate.

The layered body with a porous layer of the present invention makes gooduse of the pore properties of the porous layer, thereby being used as asubstrate material in a wide range of fields of a low-permittivitymaterial, a separator, a cushion material, an ink-image receiving sheet,an electrically insulating material, a heat insulating material, andothers. Furthermore, when a surface of the porous layer isfunctionalized, the layered body can be used as a substrate for acircuit, a heat radiating material (such as a heat sink or a heatradiating plate), an electromagnetic wave controlling material such asan electromagnetic wave shield or an electromagnetic wave absorbent, anantenna, a cell culture substratum, or some other.

The layered body with a porous layer of the present invention exhibitsexcellent printability through fine pores in the porous layer, so that afunctional material can be finely printed onto the porous layer. Thus,the layered body is useful particularly for a substrate material of thefollowing articles out of the above-mentioned articles: anelectromagnetic wave controlling material, a circuit substrate, anantenna, a heat radiating plate, and some other.

BACKGROUND ART

As a layered body composed of a base and a porous layer, for example,JP-A (i.e., Japanese Patent Application Laid-Open)-2000-143848, andJP-A-2000-158798 each disclose an ink-image receiving sheet produced bysubjecting a painted film containing a resin which is to constitute aporous layer, a solvent good for this resin, and a solvent poor thereforto a dry phase transition technique, thereby forming the porous layer.

The dry phase transition technique disclosed in the two publications isa technique of volatilizing the solvents contained in the painted filmto generate micro-phase separation. Thus, the technique has a problemthat the resin (polymeric compound), which is to constitute the porouslayer, is limited to a resin soluble in a good solvent having a lowboiling point, so that a polymeric compound large in molecular weight,which is essentially slightly soluble, cannot be used. A paintingsolution low in viscosity is preferably used in order that the polymericcompound can be dissolved therein and further a solvent therein can berapidly vaporized after the formation of the painted film; as a result,however, the following inconveniences are caused: this painted filmcannot easily have a sufficient thickness; out of constitutingcomponents of the painted film, components that are not removed when thesolvent is vaporized remain in the porous layer, so that a nonvolatileadditive is not easily usable; and the structure of the yielded porouslayer depends largely on heating conditions and production environmentalconditions in the production process, so that the porous layer is notstably produced with ease, thereby resulting in a tendency that porouslayers produced by the technique are varied in qualities, such as porediameter, rate of open area, porosity, and thickness.

In connection with a layered body composed of a base and a porous layerand produced by a technique other than the above-mentioned technique,International Publication WO98/25997 discloses a process for producing alayered body by a phase transition technique of drying a painted film ina high humidity at two stages, this film being yielded by casting a rawmaterial on a base.

According to the phase transition technique disclosed in WO98/25997,production environmental conditions can be stabilized; however, theabove-mentioned problems in the dry phase transition technique, such asa variation in film qualities, cannot be solved since the techniquebasically makes use of a heating and drying manner.

In the case of considering the usage of the layered body disclosed inWO98/25997, the inventor's investigations have made the followingevident: in the case of bonding a copper foil piece onto the layeredbody to prepare a copper clad layered plate, and then etching the plateto form a circuit pattern, it is feared that a sufficient bondingstrength can not be exhibited between the copper foil piece and thelayered body since the porous layer is weak in strength.

When the layered body disclosed in WO98/25997 is used as a cushionmaterial, the film thickness of the layered body is not easily madelarge since the layered body is formed by use of a low-viscositypainting solution. Thus, it is difficult to cause the layered body toexhibit sufficient cushion performance.

International Publication WO2007/097249 discloses a layered bodycomposed of a base and a porous layer and produced by a wet phasetransition technique.

JP-A-2004-175104 discloses a porous membrane made only of a porous layerproduced by a wet phase transition technique.

JP-A-2009-73124 discloses a layered body composed of a base and a porouslayer and produced by a wet phase transition technique, and discloses aporous membrane made only of a porous layer produced by a wet phasetransition technique.

-   Patent Literature 1: JP-A-2000-143848-   Patent Literature 2: JP-A-2000-158798-   Patent Literature 3: International Publication WO98/25997-   Patent Literature 4: International Publication WO2007/097249-   Patent Literature 5: JP-A-2004-175104-   Patent Literature 6: JP-A-2009-73124-   Patent Literature 7: JP-A-2006-237322

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

According to the wet phase transition techniques disclosed in theInternational Publication WO2007/097249, JP-A-2004-175104 andJP-A-2009-73124, many advantages as described in the following areproduced: a polymeric compound high in molecular weight, which isessentially slightly soluble, may be used; a nonvolatile additive, whichhas an advantageous effect for the formation of pores, may be used;conditions for the production environment can be stabilized so that theresultants can be stabilized in qualities; a porous layer can beproduced which is larger in thickness than porous layers produced by adry phase transition technique; a porous layer can be produced which ishigher in strength than porous layers produced by a dry phase transitiontechnique; and the porous layer can be made large in film thickness tobe improved in cushion performance.

However, the porous layer is made of a polymeric compound soluble inwater-soluble polar solvents, so that the porous layer may be dissolvedor swelled in a water-soluble polar solvent. Thus, the porous layer isnot easily used depending on the usage of the layered body.

The layered bodies disclosed in the International PublicationWO2007/097249 and JP-A-2009-73124 may each be used as a wiring board orsome other. The base and the porous layer thereof are not peeled fromeach other in an ordinary process at the time of integrating the layeredbody into a target product, or in the use of the layered body. Moreover,the adhesion between the base and the porous layer can also be madehigher by post-treatment.

However, the bonding at the interface between the base and the porouslayer depends on the bonding property which the polymer constituting theporous layer has. Thus, in applications required to be high in adhesionat the interface between the base and the porous layer, the adhesion maybe insufficient. Additionally, the porous layer itself is poorer instrength as compared with any ordinary nonporous resin since the layerhas a porous structure.

An object of the present invention is to provide a layered body whichhas a base and a porous layer on the base, is excellent in poreproperties, handleability and formability/workability and is flexible,and which has a formed crosslinked structure, thereby being alsoexcellent not only in the adhesion between the base and the porouslayer, and the film strength of the porous layer itself but also in heatresistance, chemical resistances, and endurance; and a process forproducing the layered body.

Another object of the present invention is to provide a functionallaminate using the layered body with a porous layer; and a process forproducing the functional laminate. More specifically, the object is toprovide a functional laminate in which the layered body with a porouslayer is used to form a functional layer made of a functional material,such as an electroconductive material, over the surface of the porouslayer or a polymeric layer originating from the porous layer; and aprocess for producing the functional laminate.

Means for Solving the Problems

The present invention includes the following aspects.

(1) A layered body, comprising a base, and a porous layer on at leastone surface of the base, wherein

the base is a resin film made of at least one resin material selectedfrom the group consisting of polyimide resins, polyamideimide resins,polyamide resins, and polyetherimide resins, or a metal foil piece,

the porous layer is made of a composition containing at least onepolymer selected from the group consisting of polyimide resins,polyamideimide resins, polyamide resins, and polyetherimide resins as amain component, and a crosslinking agent, and

the porous layer has fine pores having an average pore diameter of 0.01to 10 μm, and a porosity of 30 to 85%.

The polymer(s) constituting the porous layer each have a crosslinkablefunctional group. The crosslinking agent is an agent capable ofcrosslinking with the functional group of the polymer(s). For thisreason, when a heating treatment and/or an active energy ray radiatingtreatment are conducted in accordance with the crosslinking agent tocause a reaction of the crosslinking agent, a crosslinked structure isformed in the porous layer.

(2) The layered body according to item (1), wherein the crosslinkingagent is at least one selected from the group consisting of compoundseach having two or more epoxy groups, polyisocyanate compounds, andsilane coupling agents.

(3) The layered body according to item (1) or (2), wherein the porouslayer has a thickness of 0.1 to 100 μm.

(4) The layered body according to any one of items (1) to (3), whereinthe porous layer is a layer formed by casting, on the base, a solutionof a porous-layer-forming material containing the polymer, which is toconstitute the porous layer, and the crosslinking agent into a filmform, subsequently immersing this workpiece into a coagulating liquid,and next drying the workpiece.

(5) The layered body according to any one of items (1) to (4), whereinthe crosslinking agent comprised in the porous layer is in an unreactedstate.

(6) The layered body according to any one of items (1) to (4), whereinthe porous layer is a layer having a crosslinked structure formed withthe crosslinking agent.

(7) A process for producing the layered body recited in any one of items(1) to (6), comprising:

casting, on the base, a solution of a porous-layer-forming materialcontaining the polymer, which is to constitute the porous layer, and thecrosslinking agent into a film form;

subsequently immersing this workpiece into a coagulating liquid; and

next drying the workpiece.

(8) The layered body-producing process according to item (7), whereinafter the solution of the porous-layer-forming material is casted intothe film form on the base, the resultant workpiece is kept in anatmosphere having a relative humidity of 70 to 100% and a temperature of15 to 100° C. for 0.2 to 15 minutes, and then this workpiece is immersedin the coagulating liquid.

(9) A functional laminate, comprising the layered body recited in anyone of items (1) to (4), and comprising, over the surface of the porouslayer of the layered body or a polymeric layer originating from theporous layer, a functional layer selected from the group consisting ofan electroconductor layer, a dielectric layer, a semiconductor layer, anelectric insulator layer, and a resistor layer, wherein

the porous layer or the polymeric layer originating from the porouslayer has a crosslinked structure formed with the crosslinking agent.

In this specification, the polymeric layer originating from the porouslayer denotes a layer wherein the fine pores in the porous layer arelost by a crosslinking treatment for forming a crosslinked structure (aheating treatment and/or an active energy ray radiating treatment),and/or a treatment for expressing functionality of the functional layer(such as a heating treatment). The polymeric layer originating from theporous layer may be a layer transparentized by the loss of the finepores.

(10) The functional laminate according to item (9), wherein thefunctional layer is patterned.

(11) A process for producing a functional laminate comprising thelayered body recited in any one of items (1) to (4), and comprising,over the surface of the porous layer of the layered body or a polymericlayer originating from the porous layer, a functional layer selectedfrom the group consisting of an electroconductor layer, a dielectriclayer, a semiconductor layer, an electric insulator layer, and aresistor layer, comprising:

forming a layer selected from the group consisting of theelectroconductor layer, the dielectric layer, the semiconductor layer,the electric insulator layer and the resistor layer, and a precursorlayer thereof over the surface of the porous layer of the layered bodyrecited in any one of items (1) to (4); and

subjecting the resultant workpiece to a heating treatment and/or anactive energy ray radiating treatment, thereby forming a crosslinkedstructure with the crosslinking agent in the porous layer.

(12) The functional laminate according to item (11), wherein thefunctional layer is patterned.

Effects of the Invention

In the layered body with a porous layer of the present invention, theaverage pore diameter of the fine pores in the porous layer and theporosity thereof are set in the respective specific ranges so that theporous layer is excellent in flexibility. Furthermore, the porous layeris supported by the base, so that the layer is sufficient in strengthand excellent in folding endurance and handleability.

The porous layer is made of a composition containing a polymer having acrosslinkable functional group, the polymer being selected from thegroup consisting of polyimide resins, polyamideimide resins, polyamideresins, and polyetherimide resins, and a crosslinking agentcrosslinkable with the functional group. Thus, when the composition issubjected to crosslinking treatment(s), such as a heating treatmentand/or an active energy ray radiating treatment in accordance with thespecies of the crosslinking agent, a crosslinked structure is formed inthe porous layer. The formation of the crosslinked structure yields alayered body wherein the porous layer itself is excellent in filmstrength, heat resistance, chemical resistances (such as solventresistance, acid resistance and alkali resistance), and endurance.

The base is a heat-resistant resin film made of resin material(s)selected from the group consisting of polyimide resins, polyamideimideresins, polyamide resins, and polyetherimide resins, or is a metal foilpiece. Thus, the crosslinking treatment makes an improvement in theadhesion between the substrate and the porous layer. It is assumed thatcrosslinks are produced at the interface between the substrate and theporous layer. Therefore, a layered body is yielded which is excellent inthe adhesion between the substrate and the porous layer, as well as inrigidity, heat resistance, chemical resistances, and endurance.

The layered body with a porous layer of the present invention makes gooduse of the pore properties of the porous layer, thereby being used as asubstrate material in a wide range of fields of a low-permittivitymaterial, a separator, a cushion material, an ink-image receiving sheet,an electrically insulating material, a heat insulating material, andothers. Furthermore, when a surface of the porous layer isfunctionalized, the layered body can widely be used as a substrate for acircuit, a heat radiating material (such as a heat sink or a heatradiating plate), an electromagnetic wave controlling material such asan electromagnetic wave shield or an electromagnetic wave absorbent, anantenna, a cell culture substratum, or some other.

The layered body with a porous layer of the present invention exhibitsexcellent printability through fine pores in the porous layer, so that afunctional material can be finely printed onto the porous layer. Thus,the layered body is useful particularly for a substrate material of thefollowing articles out of the above-mentioned articles: anelectromagnetic wave controlling material, a circuit substrate, anantenna, a heat radiating plate, and some other.

The functional laminate of the present invention is a functionallaminate comprising the layered body with a porous layer of the presentinvention, and comprising a functional layer that may be of varioustypes over the surface of the porous layer of the layered body or apolymeric layer originating from the porous layer, wherein the porouslayer or the polymeric layer originating from the porous layer has acrosslinked structure formed with the crosslinking agent. The formationof the crosslinked structure yields a functional laminate excellent notonly in the adhesion between the substrate and the porous layer or thepolymeric layer originating from the porous layer, and the film strengthof the porous layer or the polymeric layer itself originating from theporous layer but also in heat resistance, chemical resistances, andendurance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron microscopic photograph (power: ×5000) of thesurface of a porous layer of a layered body yielded in Example 5.

FIG. 2 is an electron microscopic photograph (power: ×2000) of a crosssection of the layered body yielded in Example 5.

FIG. 3 is an electron microscopic photograph (power: ×5000) of thesurface of a porous layer of a layered body yielded in Example 16.

FIG. 4 is an electron microscopic photograph (power: ×4000) of a crosssection of the layered body yielded in Example 16.

FIG. 5 is an electron microscopic photograph (power: ×5000) of thesurface of the porous layer of a product obtained by subjecting thelayered body yielded in Example 5 to a heating treatment.

FIG. 6 is an electron microscopic photograph (power: ×2000) of a crosssection of the product obtained by subjecting the layered body yieldedin Example 5 to the heating treatment.

FIG. 7 is an electron microscopic photograph (power: ×5000) of thesurface of the porous layer of a product obtained by subjecting thelayered body yielded in Example 16 to a heating treatment.

FIG. 8 is an electron microscopic photograph (power: ×4000) of a crosssection of the product obtained by subjecting the layered body yieldedin Example 16 to the heating treatment.

FIG. 9 is an electron microscopic photograph (power: ×100) of anelectroconductive pattern yielded in Example 18.

FIG. 10 is an electron microscopic photograph (power: ×100) of anelectroconductive pattern yielded in Example 19.

FIG. 11 is an electron microscopic photograph (power: ×100) of anelectroconductive pattern yielded in Example 20.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

A description is first made about the layered body with a porous layerof the present invention (the layered body may be referred to as the“porous layer layered body” hereinafter).

The layered body with a porous layer of the present invention is alayered body having a base, and a porous layer on at least one surfaceof the base, wherein the base is a resin film made of at least one resinmaterial selected from the group consisting of polyimide resins,polyamideimide resins, polyamide resins, and polyetherimide resins, oris a metal foil piece; the porous layer is made of a compositioncontaining at least one polymer selected from the group consisting ofpolyimide resins, polyamideimide resins, polyamide resins, andpolyetherimide resins as a main component, and a crosslinking agent; andthe porous layer has fine pores having an average pore diameter of 0.01to 10 μm, and a porosity of 30 to 85%.

In the present invention, the large number of fine pores in the porouslayer may be independent fine pores, which are low in interconnection,or may be fine pores having interconnection. The average pore diameterof the fine pores in the porous layer is 0.01 to 10 μm. If the averagepore diameter is less than 0.01 μm, the porous layer is not easilyproduced by the phase separation technique according to the presentinvention. If the average pore diameter is more than 10 μm, it isdifficult to control the distribution of the pore diameter in the porouslayer evenly.

The feather that the porous layer has the large number of pores can bedetermined by observation through an electron microscope. In many cases,when the porous layer is observed from the surface thereof, it can bedetermined whether or not there are spherical empty cells, circular orelliptic pores, fibrous constructions, or some other. When a crosssection of the porous layer is observed, it can be checked whether ornot there are empty cells each surrounded by a spherical wall, or emptycells surrounded by fibrous constructions. The porous layer may be aporous layer having the surface on which a thin skin layer is formed, ora porous layer in the state that its pores are open.

The porosity (average rate of open area) of the inside of the porouslayer is 30 to 85%. If the porosity is out of this range, the porouslayer does not easily gain desired pore properties corresponding to theusage thereof. For example, if the porosity is too low, the layered bodymay be lowered in cushion property or printability. If the porosity istoo high, the layered body may be poor in strength or folding endurance.

The porous layer layered body of the present invention has anappropriate interlayer adhesion strength between the base and the porouslayer even when the crosslinking agent contained in the porous layer isin an unreacted state.

For example, when a tape peeling test based on the following method ismade about the porous layer layered body of the present invention, nointerfacial peeling is caused between the base and the porous layer: amethod of attaching, onto the surface of the porous layer of the layeredbody, a masking tape “FILM MASKING TAPE No. 603 (#25)” manufactured byTeraoka Seisakusho Co., Ltd., which has a width of 24 mm, over a lengthof 50 mm from an end of the tape; pressure-bonding the attached tapethereon with a roller (oil-resistant hard rubber roller No. 10,manufactured by Holbein Art Material Inc.), which has a diameter of 30mm and gives a load of 200 gf; and then pulling the other end of thetape at a peel rate of 50 mm/minute using a tensile tester, therebypeeling the tape into a T-shape. In other words, even when thecrosslinking agent contained in the porous layer is in an unreactedstate, the base and the porous layer are directly layered on each otherwith such an interlayer adhesion strength that no interfacial peeling iscaused therebetween in the tape peeling test.

As described above, the porous layer layered body of the presentinvention has a structure wherein the base and the porous layer arelayered on each other with the specific interlayer adhesion strengtheven in the state that the crosslinking agent contained in the porouslayer is in an unreacted state. For this reason, the layered body hasflexibility, and excellent pore properties while the layered body hasappropriate rigidity. Thus, the layered body is improved inhandleability. The interlayer adhesion strength between the base and theporous layer may be adjusted by setting appropriately the species of theraw material constituting each of the layers, or physical properties ofthe interface thereof.

In the present invention, the base is a resin film made of at least oneresin material selected from the group consisting of polyimide resins,polyamideimide resins, polyamide resins, and polyetherimide resins, oris a metal foil piece. These are each excellent in heat resistance. Thebase may be appropriately selected in accordance with the material thatconstitutes the porous layer, which will be described later.

These resin materials may be used alone or in the form of a mixture oftwo or more thereof. Copolymers (graft copolymers, block copolymers andrandom copolymers) of these resins may be used alone or in combination.Furthermore, use may be made of a polymer containing, as a main chain orside chain thereof, a skeleton (polymer chain) of any one of theabove-mentioned resins. Specific examples of the polymer include apolysiloxane-containing polyimide containing, in a main chain thereof,skeletons of a polysiloxane and a polyimide.

When a resin film is used as the base, the use of a transparent resinfilm is preferred in some cases from the viewpoint of the usage whichwill be described later. In other words, it is preferred to use atransparent resin film base in the case of desiring to convert theporous layer to a transparent polymeric layer by a heating treatment orsome other to gain a functional laminate transparent as a whole.

The transparent resin film base may be, besides a completely transparentfilm base, the so-called semitransparent film base, which permits anyobject at one side of the base to be perceivable through the base fromthe side opposite thereto. It is advisable to use, for example, a filmbase having a total light transmittance of 30 to 100%. A transparent andcolored base, such as a polyimide film, absorbs light rays having somewavelengths to be smaller in total light transmittance than completelytransparent and colorless bases. Moreover, as the thickness of the baseis increased, the total light transmittance becomes small.

The base may be a single layer, or may be a composite film composed ofplural layers made of the same raw material, or made of different rawmaterials, respectively. The composite film may be a layered film inwhich a plurality of films are layered on each other by optional use ofan adhesive or some other, or may be a film yielded through a treatmentsuch as coating, vapor deposition, or sputtering.

When the porous layer is formed on only a single surface of the base, apressure-sensitive adhesive layer may be formed on the other surface ofthe base. Furthermore, a protective film (release film) may be bondedonto the pressure-sensitive adhesive layer in order that the base caneasily be handled.

The resin base in the present invention is preferably a base about whichat the time of painting, onto a surface of the base, a solution of aporous-layer-forming material (painting solution) containing the polymerwhich is to constitute the porous layer, the resin film does not undergodissolution, intense deformation or any other change in quality, orslightly undergoes such a change.

The resin base in the present invention may be a commercially availablefilm, for example, “KAPTON” manufactured by Du Pont-Toray Co., Ltd.,“APICAL” manufactured by Kaneka Corp., “UPILEX” manufactured by UbeIndustries, Ltd., or NEOPULIM manufactured by Mitsubishi Gas ChemicalCo., Inc. as a polyimide resin film. Moreover, a product “HDN-20”manufactured by New Japan Chemical Co., Ltd. is published. Besides, thefollowing are introduced in exhibitions or others and can also be used:a product which is a transparent heat-resistant film of a polyamideimideresin and is developed by Toyobo Co., Ltd., a product of aheat-resistant transparent film (F FILM) developed by Gunze Ltd., aproduct of a transparent and colorless aramid film developed by TorayIndustries Inc., and a highly heat-resistant transparent film “SILPLUS”developed by Nippon Steel Chemical Co., Ltd.

The resin base may be subjected to a surface treatment, such as aneasy-adhesion treatment, an antistatic treatment, a sandblast treatment(sand matting treatment), a corona discharge treatment, a plasmatreatment, a chemical etching treatment, a water matting treatment, aflame treatment, an acid treatment, an alkali treatment, an oxidizingtreatment, an ultraviolet radiating treatment, or a silane couplingagent treatment. A commercially available product subjected to such asurface treatment may be used. The base is, for example, a polyimidefilm subjected to a plasma treatment.

These surface treatments may be used in combination. For example, usemay be made of a method of subjecting the base initially to any one of acorona discharge treatment, a plasma treatment, a flame treatment, anacid treatment, an alkali treatment, an oxidizing treatment, and anultraviolet radiating treatment, and then subjecting the base to asilane coupling agent treatment. Depending on the species of the base,this method may intensify the treatment degree further, as compared witha single treatment with a silane coupling agent. The method can beexpected to produce a high effect, in particular, for polyimide basesand other bases. Examples of the silane coupling agent include productsmanufactured by Shin-Etsu Chemical Co., Ltd., and Japan Energy Corp.

The thickness of the resin base is, for example, 1 to 1000 μm, usually 1to 300 μm, preferably 5 to 200 μm, more preferably 5 to 100 μm. If thethickness is too small, the base is not easily handled. On the otherhand, if the thickness is too large, the resin base may be declined inflexibility. The above-mentioned commercially available bases, theexamples of which have been given, include bases having thicknesses of12 μm, 12.5 μm, 25 μm, 50 μm, 75 μm, and 125 μm, respectively. Any oneof these bases may be used.

The material which constitutes the metal foil piece base is notparticularly limited as far as the material does not permit interfacialpeeling between the base and the porous layer in the tape peeling test.The material may be appropriately selected in accordance with thematerial which constitutes the porous layer. Examples of the materialconstituting the metal foil piece base include copper foil, aluminumfoil, iron foil, nickel foil, gold foil, silver foil, tin foil, zincfoil, and stainless steel foil.

The metal foil piece base may be a single layer, or may be a compositemetal foil piece composed of plural layers made of the same rawmaterial, or made of different raw materials, respectively. Thecomposite metal foil piece may be a layered film in which a plurality ofmetal foil pieces are layered on each other by optional use of anadhesive or some other, or may be a film yielded through a treatmentsuch as coating, vapor deposition, or sputtering. When the porous layeris formed on only a single surface of the metal foil piece base, apressure-sensitive adhesive layer may be formed on the other surface ofthe base. Furthermore, a protective film (release film) may be bondedonto the pressure-sensitive adhesive layer in order that the base caneasily be handled.

The metal foil piece base in the present invention is preferably a baseabout which at the time of painting a polymer solution (paintingsolution) that is used to form the porous layer, the film does notundergo dissolution, intense deformation or any other change in quality,or slightly undergoes such a change.

The metal foil piece base in the present invention may be a commerciallyavailable metal foil piece in a film form, examples thereof beingdescribed below.

As a copper foil piece, the following are on the market: electrolyticcopper foil pieces (article species: HTE, VP, HS, and SV) manufacturedby Fukuda Metal Foil & Powder Co., Ltd., rolled copper foil pieces(article species: RCF and RCF-AN) manufactured by the same, electrolyticcopper foil pieces (article species: HTE and VLP) manufactured by MitsuiMining & Smelting Co., Ltd., and a rolled copper foil piece manufacturedby Nippon Foil Mfg. Co., Ltd.

As an aluminum foil piece, the following are on the market: foil piecesmanufactured by Fukuda Metal Foil & Powder Co., Ltd., Nippon Foil Mfg.Co., Ltd., and Sumikei Aluminum Foil Co., Ltd., respectively.

As an iron foil piece, a piece manufactured by Toho Zinc Co., Ltd. is onthe market.

Use may be made of a product wherein a pressure-sensitive adhesive ispainted on a single surface of a metal foil piece. Examples of acommercially available product having this structure include a copperfoil pressure-sensitive adhesive tape, an aluminum foilpressure-sensitive adhesive tape, a stainless steel foilpressure-sensitive adhesive tape, an electroconductive copper foilpressure-sensitive adhesive tape, an electroconductive aluminum foilpressure-sensitive adhesive tape, and a shield pressure-sensitiveadhesive tape (electroconductive cloth pressure-sensitive adhesive tape)each manufactured by Teraoka Seisakusho Co., Ltd. A stainless steel tapeand other commercially available products manufactured by Nitoms Inc.may also be used.

The metal foil piece base may be subjected to a surface treatment, suchas a roughening treatment, an easy-adhesion treatment, an antistatictreatment, a sandblast treatment (sand matting treatment), a coronadischarge treatment, a plasma treatment, a chemical etching treatment, awater matting treatment, a flame treatment, an acid treatment, an alkalitreatment, or an oxidizing treatment. A commercially available productsubjected to such a surface treatment may be used. The metal foil piecebase is, for example, a copper foil piece subjected to a rougheningtreatment.

The thickness of the metal foil piece base is, for example, 1 to 1000μm, usually 1 to 300 μm, preferably 5 to 200 μm, more preferably 5 to100 μm. If the thickness is too small, the base is not easily handled.On the other hand, if the thickness is too large, the metal foil piecebase may be declined in flexibility. The above-mentioned commerciallyavailable bases, the examples of which have been given, include baseshaving thicknesses of 9 μm, 12 μm, 18 μm, 35 μm, and 70 μm,respectively. Any one of these bases may be used.

The resin film base and the metal foil piece base may each be a base inwhich a through hole is made. The wording “base in which a through holeis made” herein means a base having an open hole penetrating the base ina direction substantially perpendicular to planes of the base. The basethat is a base having many through holes is not particularly limited asfar as the base is one wherein a large number of through holes are madeand no interfacial peeling is caused between the base and the porouslayer in the above-mentioned tape peeling test. Examples thereof includea punched film; and metal foil pieces or sheets, such as a punchedmetal, an expanded metal, and an etched metal. An appropriate base isselected in accordance with properties such as water resistance, heatresistance, and chemical resistances.

The punched film may be a film wherein holes having a shape such as acircle, square, rectangle, or ellipse are made in a film made of apolyimide or some other by subjecting this original film to punching orsome other working.

The punched metal may be a metal wherein holes having a shape such as acircle, square, rectangle, or ellipse are made in a metal foil piece orsheet by subjecting this piece or sheet to punching or some otherworking. Examples of the material thereof include iron, aluminum,stainless steel, copper, and titanium.

The expanded metal may be a metal having a shape according to the JISstandard. Examples thereof include XS63 and XS42 flat metals. Examplesof the material thereof include iron, aluminum, and stainless steel.

The base having many through holes may be produced by any usual method,for example, a working method such as etching, punching or laserradiation in accordance with the material. The base having many throughholes has the following advantage: when a polymer solution (a solutionof a porous-layer-forming material) is painted onto a surface thereof tolaminate a porous layer thereon, the polymer solution advances also intothe through holes; thus, they can be layered on each other with anexcellent interlayer adhesion strength. Moreover, the base hasflexibility and excellent pore properties while the base has appropriaterigidity. Thus, the base can gain an effect of an improvement inhandleability.

When the base is a punched film or punched metal, the rate of open areain the surface thereof is about 20 to 80%, preferably about 30 to 70%.If the numerical value of the rate of open area in the surface is toolow, the base is unfavorably liable to become poor in permeability togas or liquid. If the numerical value is too high, the base unfavorablytends to be declined in strength to be poor in handleability.

When the base is an expended metal, the rate of open area in the surfacethereof is about 20 to 80%, preferably about 25 to 70%. If the numericalvalue of the rate of open area in the surface is too low, the base isunfavorably liable to become poor in permeability to gas or liquid. Ifthe numerical value is too high, the base unfavorably tends to be easilydeclined in strength to be poor in handleability.

In the present invention, the porous layer is made of a compositioncontaining at least one polymer having a crosslinkable functional groupand selected from the group consisting of polyimide resins,polyamideimide resins, polyamide resins, and polyetherimide resins as amain component, and further containing a crosslinking agentcrosslinkable with the functional group. These polymer components areexcellent in heat resistance, thermally shapeable, and excellent inmechanical strength, chemical resistances, and electric properties.

Examples of the crosslinkable functional group contained in thepolymer(s) include amide, carbonyl, amino, isocyanate, hydroxyl, epoxy,aldehyde, and acid anhydride groups. The number of the species of thesefunctional groups contained in the polymer(s) is not limited.

Usually, the polyamideimide resins may each be produced by conductingpolymerization through a reaction between trimellitic anhydride and adiisocyanate, or a reaction between anhydrous trimellitic chloride and adiamine, and then imidizing the resultant polymer. Since thepolyamideimide resin has many amide groups in the molecule, these groupscan each be preferably used as the crosslinkable functional group. Thereexists a polyamideimide resin about which imides are partially in thestate of an unreacted precursor (an amic acid) so that the reactivity ofthe resin remains. An amide group or carboxyl group that constitutesthis amic acid may be used as the crosslinkable functional group. Asdescribed above, the polyamideimide resin may be produced by conductingpolymerization through a reaction between trimellitic anhydride and adiisocyanate, or a reaction between anhydrous trimellitic chloride and adiamine; thus, in many cases, at a terminal of the polyamideimide, acarboxyl group, an isocyanate group, an amino group or some otherremains. This group may be used as the crosslinkable functional group.

The polyimide resins may each be produced, for example, by causing atetracarboxylic acid component to react with a diamine component toyield a polyamic acid (polyimide precursor), and further imidizing theacid. When the porous layer is made of the polyimide resin, theimidization of the starting compound makes the solubility of theresultant compound poor. It is therefore advisable that a porous film isinitially formed at the stage of the polyamic acid and then the film isimidized (for example, thermally imidized or chemically imidized). Theprecursor has, in any molecule thereof, many carboxyl groups or amidegroups; thus, the groups can each be preferably used as thecrosslinkable functional group. In the same manner as in the case of thepolyamideimide resin, in many cases, at a terminal of the polyimide, acarboxyl group, an amino group or some other remains. This group mayalso be used as the crosslinkable functional group.

The polyamide resins can each be produced by polycondensation between adiamine and a dicarboxylic acid, ring-opening polymerization of alactam, polycondensation of an aminocarboxylic acid, or some other. Thepolyamide resin may be an aromatic polyamide resin. The resin has, inany molecule thereof, many amide groups; thus, the groups may each beused as the crosslinkable functional group. In the same manner as in thecase of the polyamideimide resin, in many cases, at a terminal of thepolyamide, a carboxyl group, an amino group or some other remains. Thisgroup may be used as the crosslinkable functional group.

The polyetherimide resins can each be produced, for example, by causingan aromatic tetracarboxylic acid component having an ether bond to reactwith a diamine component to yield a polyamic acid, and further imidizingthe acid. Any amide group or carboxyl group that constitutes this amicacid can be used as the crosslinkable functional group. In the samemanner as in the case of the polyamideimide resin, in many cases, at aterminal of the polyetherimide resin, a carboxyl group, an isocyanategroup, an amino group or some other remains. This group may also be usedas the crosslinkable functional group.

As described above, the crosslinkable functional group may be present inthe precursor of the above-mentioned polymer(s). Any imide resin (apolyimide resin, a polyamideimide resin, or a polyetherimide resin) canbe produced in the state of a precursor (amic acid) wherein its imidegroup moieties are wholly unreacted, or in the state of a precursor(amic acid) wherein its imide group moieties are partially unreacted.Actually, some imide resins are sold in such a form. In general, an amicacid is heated to be converted to an imide, and the resultant imide isused as an imide resin. In the present invention, any amide group orcarboxyl group that constitutes this precursor amic acid may be used asthe crosslinkable functional group.

Moreover, by modifying a polyimide resin, a polyamideimide resin, apolyamide resin or a polyetherimide resin, the crosslinkable functionalgroup may be introduced into the resin.

The crosslinkable functional group may be present in the main chain ofthe resin(s), or may be present in a side chain thereof. Thecrosslinkable functional group may be present in the middle of themolecular chain thereof, or at a terminal thereof. The crosslinkablefunctional group may be present in a benzene ring contained in thepolymer(s).

The above-mentioned polymer components may be used alone or incombination of two or more thereof. Copolymers (graft copolymers, blockcopolymers or random copolymers) of the above-mentioned resins may beused alone or in combination. Furthermore, use may be made of a polymercontaining, in its main chain or side chain, a skeleton (polymer chain)of any one of these resins. Specific examples of such a polymer includea polysiloxane-containing polyimide that contains, in the main chainthereof, skeletons of a polysiloxane and a polyimide. Any amide group orcarboxyl group that constitutes an amic acid of a polyimide precursorthereof may be used as the crosslinkable functional group.

In the present invention, besides the polyimide resins, thepolyamideimide resins, the polyamide resins, and the polyetherimideresins, a different resin may be together used in a small amount as faras properties of these amide or imide resins are not damaged. Examplesof the different resin include polyethersulfone resins, polycarbonateresins, polyphenylenesulfide resins, polyester resins, liquidcrystalline polyester resins, polybenzoxazole resins, polybenzoimidazoleresins, polybenzothiazole resins, polysulfone resins, cellulose resins,and acrylic resins.

The crosslinking agent is an agent that can react with the crosslinkablefunctional group which the polymer(s) have so as to crosslink therewith.Examples of the crosslinking agent include any compound having two ormore epoxy groups, polyisocyanate compounds, and silane coupling agents.

The compound having two or more epoxy groups can react with thecrosslinkable functional group (an amide, carboxyl, amino, isocyanate,hydroxyl, epoxy, aldehyde, or acid anhydride group) which the polymer(s)have. The compound having two or more epoxy groups is generally calledan epoxy resin in many cases.

The epoxy resin can be classified into various resins, example of whichinclude glycidyl ether epoxy resins, for example, bisphenol resins, suchas bisphenol A type and bisphenol F type resins, and novolak resins,such as phenol novolak type and cresol novolak type resins; alicyclicepoxy resins; and modified resins of these resins. Examples of a usablecommercially available product of the epoxy resin include “ARALDITE”manufactured by Huntsman Advanced Materials, “DENACOL” manufactured byNagase ChemteX Corp., “CELLOXIDE” manufactured by Daicel ChemicalIndustries, Ltd., “EPOTOHTO” manufactured by Tohto Kasei Co., Ltd., and“j ER” manufactured by Japan Epoxy Resins Co., Ltd.

The above-mentioned polyisocyanate compounds can each react with thecrosslinkable functional group (a carboxyl, amino, hydroxyl, epoxy oracid anhydride group) which the polymer(s) have. Examples of thepolyisocyanate compound include aromatic polyisocyanate compounds suchas tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI),phenylene diisocyanate, diphenyl diisocyanate, and naphthalenediisocyanate; aliphatic polyisocyanate compounds such as hexamethylenediisocyanate (HDI), and lysine diisocyanate; and alicyclicpolyisocyanate compounds such as isophorone diisocyanate (IPDI),cyclohexane-1,4-diisocyanate, and hydrogenated MDI. Examples of acommercially available product of the polyisocyanate compound include“TAKENATE” manufactured by Mitsui Chemicals Polyurethanes, Inc., and“COLONATE” manufactured by Nippon Polyurethane Industry Co., Ltd.

The above-mentioned silane coupling agents can each react with thecrosslinkable functional group (an amide, carboxyl, amino, isocyanate,hydroxyl, epoxy, aldehyde, or acid anhydride group) which the polymer(s)have. Examples of the silane coupling agent includeN-2(aminoethyl)3-aminopropylmethyldimethoxysilane and3-glycidoxypropyltriethoxysilane. Silane coupling agents manufactured byShin-Etsu Chemical Co., Ltd. may be used. In the case of using a metalfoil piece base, the silane coupling agent is effective for improvingthe adhesion between the porous layer and the metal foil piece base.Also in the case of using a surface-treated resin film base, the silanecoupling agent is effective for improving the adhesion between theporous layer and the resin film base.

Examples other than the above-mentioned examples of the crosslinkingagent include a melamine resin, a phenol resin, a urea resin, aguanamine resin, an alkyd resin, a dialdehyde compound, and an acidanhydride.

The melamine resin can react with the crosslinkable functional group (anamino, hydroxyl, or aldehyde group) which the polymer(s) have. Examplesof the melamine resin include “YUBAN 20SB” manufactured by MitsuiChemicals, Inc., and “SUPER BACKAMINE” manufactured by DIC Corp.

The phenol resin can react with the crosslinkable functional group (acarboxyl, amino, hydroxyl, epoxy, isocyanate, aldehyde or acid anhydridegroup) which the polymer(s) have. Examples of the phenol resin include“SUMILITERESIN” manufactured by Sumitomo Bakelite Co., Ltd.

The urea resin can react with the crosslinkable functional group (anamino, hydroxyl, or aldehyde group) which the polymer(s) have. Examplesof the urea resin include “UBAN 10S60” manufactured by Mitsui Chemicals,Inc.

The guanamine resin can react with the crosslinkable functional group(an aldehyde group) which the polymer(s) have. Examples of the guanamineresin include “NIKALAC BL-60” manufactured by Sanwa Chemical Co., Ltd.

The alkyd resin can react with the crosslinkable functional group (acarboxyl, hydroxyl, epoxy, isocyanate, or acid anhydride group) whichthe polymer(s) have. Examples of the alkyd resin include “BECKOSOL”manufactured by DIC Corp.

The dialdehyde compound can react with the crosslinkable functionalgroup (an amino or hydroxyl group) which the polymer(s) have. Examplesof the dialdehyde compound include glyoxal.

The acid anhydride can react with the crosslinkable functional group (anamino, epoxy or isocyanate group) which the polymer(s) have. Examples ofthe acid anhydride include tetrahydrophthalic anhydride (THPA),hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride(Me-THPA), methylhexahydrophthalic anhydride (Me-HHPA), methyl nadicanhydride (NMA), hydrogenated methyl nadic anhydride (H-NMA),trialkyltetrahydrophthalic anhydride (TATHPA),methylcyclohexenetetracarboxylic dianhydride (MCTC), phthalic anhydride(PA), trimellitic anhydride (TMA), pyromellitic anhydride (PMDA),benzophenonetetracarboxylic dianhydride (BTDA), ethylene glycolbisanhydrotrimellitate (TMEG), glycerin bis(anhydrotrimellitate)monoacetate (TMTA), dodecenylsuccinic anhydride (DDSA), aliphaticdibasic acid polyanhyride, and chlorendic anhydride.

In the present invention, it is advisable to select the crosslinkingagent in accordance with the species of the used polymer(s), consideringthe reactivity thereof. About the crosslinking agent, a single speciesthereof or a combination of two or more species thereof may be used.

The method for causing the crosslinkable functional group in thepolymer(s) to react with the crosslinking agent may be a physicaltreatment with heat, or the radiation of active energy rays (visiblerays, ultraviolet rays, an electron beam, or radioactive rays). A heattreatment is preferably used since the treatment is simple and easy. Theradiation of active energy rays such as ultraviolet rays, an electronbeam, or radioactive rays is also preferably used since the radiationcan give a large energy in a short period to promote the reaction.Although the reaction of the crosslinking agent may be advanced in theabsence of any catalyst, the reaction may be promoted by the addition ofa catalyst.

In the composition constituting the porous layer, the blend ratiobetween the polymer(s) having the crosslinkable functional group and thecrosslinking agent crosslinkable with the functional group is notparticularly limited, and may be appropriately decided, considering adesired degree of crosslinking, the species of the polymer(s) and thecrosslinking agent, the reactivity between the functional group and thecrosslinking agent, the adhesion between the porous layer and the base,and others. For example, it is advisable to set the amount of thecrosslinking agent 2 to 312.5 parts by weight for 100 parts by weight ofthe polymer(s). If the amount of the crosslinking agent is less than 2parts by weight for 100 parts by weight of the polymer(s), the degree ofcrosslinking would be small. If the amount of the crosslinking agent ismore than 312.5 parts by weight for 100 parts by weight of thepolymer(s), the crosslinking agent becomes excessive in amount so that aportion of the crosslinking agent that does not contribute to thecrosslinking reaction may remain in the porous layer after the layer issubjected to a crosslinking treatment. In connection with the lowerlimit amount of the crosslinking agent, the amount of the crosslinkingagent is preferably 10 parts by weight or more, more preferably 20 partsby weight or more for 100 parts by weight of the polymer(s). Inconnection with the upper limit amount of the crosslinking agent, theamount of the crosslinking agent is preferably 200 parts by weight orless, more preferably 150 parts by weight or less for 100 parts byweight of the polymer(s).

The thickness of the porous layer is, for example, 0.1 to 100 μm,preferably 0.5 to 70 μm, more preferably 1 to 50 μm. If the thickness istoo small, the porous layer is not stably produced with ease. Moreover,the layered body may be declined in cushion performance, orprintability. On the other hand, if the thickness is too large, the porediameter distribution is not evenly controlled with ease.

In the porous layer layered body of the present invention, the base andthe porous layer are directly layered onto each other, withoutinterposing any other layer therebetween, with such an interlayeradhesion strength that no interfacial peeling is caused in the tapepeeling test even when the crosslinking agent contained in the porouslayer is in an unreacted state. In the process for producing the porouslayer layered body, or in the state that the crosslinking agent isunreacted, examples of means for improving the adhesion between the baseand the porous layer include a method of subjecting a surface of thebase on which the porous layer is to be layered to an appropriatesurface treatment, such as a sandblast treatment (sand mattingtreatment), a corona discharge treatment, an acid treatment, an alkalitreatment, an oxidizing treatment, an ultraviolet radiating treatment, aplasma treatment, a chemical etching treatment, a water mattingtreatment, a flame treatment, or a silane coupling agent treatment; anda method of using, as components constituting the base and the porouslayer, a combination of raw materials that are able to exhibit goodadhesion (affinity or compatibility). The silane coupling agent may beany one of the above-mentioned examples thereof. These surfacetreatments may be applied in combination of two or more thereof.Depending on the base, it is preferred to apply a combination of asilane coupling agent treatment with some other treatment.

From the viewpoint of the adhesion between the base and the porouslayer, it is preferred that the components constituting the base arepartially or wholly identical with those constituting the porous layer.A structure therefor is, for example, a structure wherein monomer unitsof the respective polymeric compounds constituting the base and theporous layer are at least partially common to each other. Examples ofthe structure include a layered body wherein materials constituting thebase and the porous layer are any one of the following combinations:polyimide/polyimide, polyamideimide/polyimide, polyimide/polyamideimide,polyetherimide/polyimide, polyimide/polyetherimide,polyamideimide/polyetherimide, polyetherimidelpolyamideimide,polyamide/polyimide, polyamideimide/polyamide, and polyimide/polyamide.

The porous layer in the present invention has many fine pores, and theaverage pore diameter of the fine pores (the average pore diameter ofthe fine pores in the porous layer) is 0.01 to 10 μm, preferably 0.05 to5 μm. If the average pore diameter is out of this range, the porouslayer is poor in pore properties since the layer does not easily producea desired effect in accordance with the usage. If the average porediameter is smaller than 0.01 μm, the layered body may be declined incushion performance or heat insulating performance and further theporous layer is not easily produced according to the phase separationtechnique in the present invention. On the other hand, if the averagepore diameter is more than 10 μm, the pore diameter distribution in theporous layer is not evenly controlled with ease. Thus, the relativepermittivity of the porous layer may become uneven between individualregions thereof.

The average rate of open area (porosity) of the inside of the porouslayer is, for example, 30 to 85%, preferably 35 to 85%, more preferably40 to 85%. If the porosity is out of this range, the porous layer doesnot easily gain desired pore properties corresponding to the usage. Ifthe porosity is, for example, too low, the layered body may be raised inpermittivity, or be lowered in cushion performance, heat insulatingperformance or printability. If the porosity is too high, the layeredbody may be poor in strength or folding endurance.

The rate of open area in the surface (rate of surface open area) of theporous layer is, for example, 90% or less (for example, 0 to 90%),preferably about 0 to 80%. If the rate of surface open area is too high,the layered body may be unfavorably declined in mechanical strength orfolding endurance with ease. Depending on the usage, there is generateda case where it is preferred that the rate of surface open area of theporous layer is high, or a case where it is preferred that the rate ofsurface open area is low.

For example, when the porous layer is bonded to a copper foil piece toproduce a copper clad layered plate, the base of which is low inrelative permittivity, an adhesive therefor penetrates through theinside at the time of the bonding onto the copper foil piece, so thatthe adhesive may unfavorably make the layered plate low in relativepermittivity. When the layered plate is further etched to form acircuit, an etchant therefor penetrates into the porous layer so thatthe porous layer may be unfavorably etched from the inside. Thus, it ispreferred that the rate of surface open area is low.

For example, when the surface of the porous layer is plated or printed,an appropriate open area is preferred for causing the layer to exhibitan anchor effect to keep, with certainty, the adhesion between thesurface and the plating or the ink. Moreover, an appropriate open areamay be preferred for washing sufficiently a water-soluble polar solventor water-soluble polymer used in the formation of the porous layer.

The porous layer needs only to be formed on at least one surface of thebase. The porous layer may be formed on each of both surfaces thereof.According to the formation of the porous layer onto each of the basesurfaces, good use is made of the pore properties thereof to yield aporous layer layered body which has, in each of both surfaces thereof, alow-permittivity property, cushion property, heat insulatingperformance, good printability, and others. When the surface of theporous layer is further functionalized, the resultant may be used as asubstrate material in a wide range of fields of a substrate for acircuit, a heat radiating material (a heat sink or a radiating plate),an electromagnetic wave controlling material such as an electromagneticwave shield or an electromagnetic wave absorbent, a low-permittivitymaterial, an antenna, a separator, a cushion material, an ink-imagereceiving sheet, an electrically insulating material, a heat insulatingmaterial, a cell culture substratum, an electrolytic membrane base, andothers.

The porous layer layered body of the present invention can be producedby, for example,

a process of casting, on a base as described above, a solution of aporous-layer-forming material containing a polymer which is toconstitute a porous layer as described above, and a crosslinking agentinto a film form; bringing this workpiece into contact with acoagulating liquid, thereby subjecting the workpiece to aporousness-imparting treatment; and then drying the workpiece as it is,thereby yielding the layered body, which is composed of the base and theporous layer; or

a process of casting, on a support, a solution of a porous-layer-formingmaterial containing a polymer which is to constitute a porous layer asdescribed above into a film form; bringing this workpiece into contactwith a coagulating liquid, thereby subjecting the workpiece to aporousness-imparting treatment; transferring the resultant porous layerfrom the support to a surface of a base; and subsequently drying theresultant workpiece, thereby yielding the layered body, which iscomposed of the base and the porous layer. In the present invention, theformer process is preferably used, as will be described below.

The process of the present invention for producing a porous layerlayered body is characterized by casting, on a base as described above,a solution of a porous-layer-forming material containing a polymer whichis to constitute a porous layer as described above, and a crosslinkingagent into a film form; subsequently introducing this workpiece into acoagulating liquid; and next drying the workpiece, thereby laminatingthe porous layer onto at least one surface of the base to yield theporous layer layered body. According to this process, a wet phasetransition technique is used to form the porous layer onto the base, andthen the workpiece is dried as it is. For this reason, at the same timewhen the porous layer is formed, the porous layer can be layered andadhered closely onto the base surface. Thus, the efficiency of theproduction can be improved. A porous layer having many fine pores isflexible so that the porous layer alone is not easily handled; thus, thestep of laminating the layer is difficult. However, the productionprocess of the present invention, wherein the film is layered at thesame time when the film is formed, makes it possible to avoid such aproblem and yield, with ease, a porous layer layered body wherein a baseand a porous layer having excellent pore properties are directly layeredonto each other.

The solution of the porous-layer-forming material, which may be referredto as the porous-layer-forming solution hereinafter, contains, forexample, polymer component(s) that are to be a main material whichconstitutes the porous layer, a crosslinking agent, and a water-solublepolar solvent, and optionally contains a water-soluble polymer andwater.

In the porous-layer-forming solution, instead of the polymercomponent(s), which are to constitute the porous layer, the followingmay be used: a monomer component (raw material) of the polymercomponent(s), an oligomer thereof, a precursor thereof that has not beenyet imidized or cyclized, or some other.

The temperature of the coagulating liquid is not particularly limited,and is, for example, 0 to 100° C. If the temperature of the coagulatingliquid is lower than 0° C., the washing effect of the solvent or someother is easily declined. If the temperature of the coagulating liquidis higher than 100° C., the solvent or the coagulating liquid vaporizesso that the working environment is damaged. The coagulating liquid ispreferably water from the viewpoint of costs, safety, toxicity andothers. When the coagulating liquid is water, the temperature of wateris appropriately about 5 to 60° C. The period of immersion of theworkpiece in the coagulating liquid is not particularly limited, and itis advisable to select appropriately a period over which the solvent andthe water-soluble polymer are sufficiently washed. If the washing periodis too short, the porous structure may be broken with a remainingportion of the solvent in the drying step. If the washing period is toolong, the production efficiency is declined so that production costsincrease. The washing period cannot be specified without reservationsince the period depends on the thickness of the porous layer, andothers, and may be set into the range of about 0.5 to 30 minutes.

It is preferred to cast the porous-layer-forming solution into a filmform onto a base, keep the workpiece in an atmosphere having a relativehumidity of 70 to 100% and a temperature of 15 to 100° C. for 0.2 to 15minutes, and subsequently immerse this workpiece into the coagulatingliquid.

The addition of the water-soluble polymer or water to theporous-layer-forming solution is effective for making the film structureinto a sponge form, thereby making it porous. Examples of thewater-soluble polymer include polyethylene glycol, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, polyacrylic acid,any polysaccharide, and derivatives thereof; and mixtures thereof. Ofthese examples, polyvinyl pyrrolidone is preferred since the polymerrestrains the formation of fine pores inside the porous layer and makesan improvement in the mechanical strength of the porous layer. Thesewater-soluble polymers may be used alone or in combination of two ormore thereof. The weight-average molecular weight of the water-solublepolymer is appropriately 200 or more, preferably 300 or more, inparticular preferably 400 or more (for example, about 400 to 200000),and may be 1000 or more for making the workpiece porous. The addition ofwater makes it possible to adjust the pore diameter. For example, whenthe addition amount of water into the porous-layer-forming solution isincreased, the pore diameter can be made large.

The water-soluble polymer is very effective for rendering the filmstructure a homogenous sponge-like porous structure. Various structurescan be yielded by varying the species and the amount of thewater-soluble polymer. Thus, the water-soluble polymer is very suitablefor giving desired pore properties to the porous layer as an additiveused when the layer is formed.

However, the water-soluble polymer is an unnecessary component to beremoved, which does not constitute the porous layer finally. In theprocess of the present invention using a wet phase transition technique,the water-soluble polymer is washed to be removed in the step in whichthe water-soluble polymer is immersed in the coagulating liquid such aswater to undergo phase transition. On the other hand, in a dry phasetransition technique, a component which does not constitute any porouslayer (unnecessary component) is heated to be removed, and awater-soluble polymer is usually unsuitable for being heated andremoved; thus, it is very difficult to use the polymer as an additive inthe technique. As described herein, it is difficult to form various voidstructures by a dry phase transition technique while the productionprocess of the present invention is advantageous since a porous layerlayered body having desired pore properties can easily be produced.

However, when the amount of the water-soluble polymer is increased, theinterconnection of the pores tends to be heightened. Thus, when theinterconnection is desired to be low, it is preferred to set the amountof the water-soluble polymer into a minimum amount. When theinterconnection is heightened, the porous layer tends to be lowered instrength. Thus, it is not preferred to add the water-soluble polymerexcessively. Furthermore, the excessive addition is not preferred sincethe addition produces a necessity of making the period for the washinglong. It is allowable not to use any water-soluble polymer.

Examples of the water-soluble polar solvent include dimethylsulfoxide,N,N-dimethylformamide, N,N-dimethylacetamide (DMAc),N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, and γ-butyrolactone; andmixtures thereof. Use may be made of a solvent having solubility inaccordance with the chemical skeleton of resin(s) used as the polymercomponent(s) (i.e., a good solvent for the polymer component(s)).

The blend amount of each of the components in the porous-layer-formingsolution is preferably as follows: the blend amount of the polymercomponent(s) is 8 to 25% by weight of the porous-layer-forming solution;that of the crosslinking agent 0.5 to 25% by weight thereof; that of thewater-soluble polymer 0 to 50% by weight thereof; that of water 0 to 10%by weight thereof; and that of the water-soluble polar solvent 30 to 82%by weight thereof. If the concentration of the polymer component(s) istoo low at this time, the porous layer becomes insufficient in thicknessor does not easily gain desired pore properties. On the other hand, ifthe concentration of the polymer component(s) is too high, the porositytends to be small. If the concentration of the crosslinking agent is toolow, the porous layer does not easily gain a sufficient effect of makingan improvement in chemical resistances or in adhesion to the base. Onthe other hand, if the concentration of the crosslinking agent is toohigh, the resultant porous layer is liable to have a sticky surface, andafter the crosslinking thereof an excessive portion of the crosslinkingagent may remain. If the concentration of the water-soluble polymer istoo high, the solubility of the individual components in theporous-layer-forming solution deteriorates, the porous layer is declinedin strength, and other inconveniences are easily caused. The additionamount of water may be used for the adjustment of the pore diameter.When the addition amount is increased, the pore diameter can be madelarge.

It is desired to cast the porous-layer-forming solution into a film formonto a base, keep the resultant film in an atmosphere having a relativehumidity of 70 to 100% and a temperature of 15 to 100° C. for 0.2 to 15minutes, and subsequently introduce the workpiece into a coagulatingliquid made of a nonsolvent for the polymer component(s). When the castfilm-form product is put under the humidifying condition, a porous layerhigh in homogeneity is easily obtained. It appears that when the productis put under the humidifying condition, water invades the inside of thefilm from the surface thereof to promote the phase separation of thepolymer solution efficiently. The condition is preferably a conditionthat the relative humidity is 90 to 100% and the temperature is 30 to80° C., more preferably a condition that the relative humidity is about100% (for example, 95 to 100%) and the temperature is 40 to 70° C. Ifthe water content in the air is smaller than this humidity, the porositymay become insufficient.

The above-mentioned process makes it possible to form, with ease, forexample, a porous layer having many fine pores having an average porediameter of 0.01 to 10 μm. As described above, about the porous layerconstituting the porous layer layered body in the present invention, thediameter of the fine pores, the porosity, and the rate of open area caneach be adjusted into a desired value by selecting appropriately therespective species or amounts of the constituting components of thepolymer solution, the use amount of water, the humidity and thetemperature in the casting, the period for the casting, and others.

The coagulating liquid used in the phase transition technique needs onlyto be a solvent for coagulating the polymer component(s), and isappropriately selected in accordance with the species of the polymer(s)used as the polymer component(s). The liquid may be, for example, asolvent for coagulating a polyamideimide resin, a polyamic acid, or someother. The liquid may be, for example, a water-soluble coagulatingliquid, examples of which include water; alcohols such as a monohydricalcohol such as methanol or ethanol, or a polyhydric alcohol such asglycerin; water-soluble polymers such as polyethylene glycol; andmixtures thereof.

In the production process of the present invention, after theintroduction of the workpiece into the coagulating liquid to form theporous layer onto the base surface, the resultant is dried as it is,thereby producing a layered body having a structure wherein the porouslayer is directly layered on the surface of the base. The drying is notparticularly limited as far as the drying is according to a methodcapable of removing the solvent component(s) in the coagulating liquidand the others. The drying may be drying by heating or natural drying atroom temperature. The drying treatment at this time is conducted at atemperature lower than the glass transition temperature (Tg) of thecomposition constituting the porous layer. In the drying treatment,attention should be paid not to cause a phenomenon that the compositionconstituting the porous layer is softened so that the fine poresdisappear. If the fine pores disappear, the upper of the porous layer isdeteriorated in printability.

The method for the drying treatment is not particularly limited, and maybe a hot wind treatment, a thermal roll treatment, or a method ofputting the workpiece into a thermostat, an oven or the like. The methodneeds only to control the layered body into a predetermined temperature.The atmosphere in the drying treatment may be the air, nitrogen, or aninert gas. The use of the air is most inexpensive; however, the use mayinvolve an oxidizing reaction. When this should be avoided, it ispreferred to use nitrogen or an inert gas. Nitrogen is suitable from theviewpoint of costs. Conditions for the heating are appropriately setconsidering the productivity, physical properties of the porous layerand the base, and others. When the workpiece is dried, a layered bodycan be yielded wherein the porous layer is directly shaped on the basesurface.

The resultant porous layer layered body is subjected to a crosslinkingtreatment. In the porous layer layered body yielded as described above,the crosslinking agent contained in the porous layer is usually in anunreacted state. However, when the crosslinking agent is an agentcausing thermal crosslinkage, a crosslinked structure may be formed by apartial or entire reaction of the crosslinking agent depending on thedrying treatment condition.

The crosslinking treatment may be a heating treatment, and/or an activeenergy ray (visible rays, ultraviolet rays, an electron beam,radioactive rays or some other) radiating treatment. It is advisable toset appropriate conditions for each of these treatments. For example, inthe heating treatment, it is advisable to set the following conditions:a temperature of 100 to 400° C., and a period of 10 seconds to 5 hours.

When the crosslinking treatment is conducted, the crosslinkablefunctional group of the polymer(s) reacts with the functional group ofthe crosslinking agent to form a crosslinked structure in the porouslayer. By the formation of the crosslinked structure, a layered body isyielded which is very good in the film strength of the porous layeritself as well as in heat resistance, chemical resistances, andendurance. It appears that crosslinks are formed also in the interfacebetween the substrate and the porous layer to improve the adhesionbetween the substrate and the porous layer. A layered body is yieldedwhich is far better in the adhesion between the substrate and the porouslayer, as well as in rigidity.

When a functional layer is further laid onto the surface of the porouslayer (functionalizing treatment) to yield a functional laminate of thepresent invention, there are several timings for conducting thecrosslinking treatment, as described below.

(a) A method of subjecting the resultant porous layer layered body tothe crosslinking treatment, and subsequently laying the functional layeronto the porous layer surface to yield the functional laminate.

(b) A method of laying the functional layer onto the porous layersurface of the resultant porous layer layered body, and subsequentlysubjecting the workpiece to the crosslinking treatment. The crosslinkingtreatment that is a crosslinking treatment by heating may also attain aheating treatment for expressing the function of the functional layer.

(c) A method of subjecting the resultant porous layer layered body to apartial-crosslinking treatment, subsequently laying the functional layeronto the porous layer surface, and further subjecting the workpieceagain to a crosslinking treatment to attain a complete crosslinkingtreatment, thereby yielding the functional laminate. The partialcrosslinking treatment referred to herein intends the porous layer to beturned into a semi-cured state (the so-called B stage).

The production process of the present invention makes it possible toyield easily a layered body including a base, and a porous layer whichis laid on a single surface of the base, or each of both surfacesthereof and which is made of a composition containing polymer(s) and acrosslinking agent wherein the porous layer has fine pores having anaverage pore diameter of 0.01 to 10 μm, and has a porosity of 30 to 85%.

If necessary, the porous layer layered body of the present invention maybe subjected to a heat treatment or a coat-forming treatment to give adesired property thereto.

The porous layer layered body of the present invention has the formedcrosslinked structure, thereby being very good in chemical resistances.The porous layer may be further subjected to achemical-resistance-imparting treatment. In various use forms of theporous layer layered body, the impartation of the chemical resistancesto the porous layer makes it possible that the layered bodyadvantageously avoids interlayer peeling, swelling, dissolution,denaturation, and other inconveniences when brought into contact with asolvent, an acid, an alkali or some other. Thechemical-resistance-imparting treatment may be, for example, a physicaltreatment with heat, ultraviolet rays, visible rays, an electron beam,radioactive rays, or some other; or a chemical treatment of coating theporous layer with a chemical-resistant polymeric compound.

The chemical referred to herein denotes a known substance which causes aresin constituting any porous film in the prior art to be dissolved,swelled, shrunken, or decomposed to decline a function of the film as aporous film. In accordance with the species of the porous layer, andthat of the resin that constitutes the base, the chemical may be ofvarious species. Thus, the chemical is not specified withoutreservation. Specific examples of the chemical include intensely polarsolvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF),N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP),2-pyrrolidone, cyclohexanone, acetone, methyl acetate, ethyl acetate,ethyl lactate, acetonitrile, methylene chloride, chloroform,tetrachloroethane, and tetrahydrofuran (THF); inorganic salts such assodium hydroxide, potassium hydroxide, calcium hydroxide, sodiumcarbonate, and potassium carbonate; amines such as triethylamine; anaqueous solution wherein an alkali such as ammonia is dissolved, or analkaline organic-solvent solution; inorganic acids such as hydrogenchloride, sulfuric acid, and nitric acid; an aqueous solution wherein anacid, for example, an organic acid (such as acetic acid, phthalic acidor any other organic acid having a carboxylic acid) is dissolved, or anacidic organic-solvent solution; and mixtures thereof.

The chemical-resistant polymeric compound is not particularly limited asfar as the compound is a compound very resistant against intensely polarsolvents, alkalines, acids, and other chemicals. Examples thereofinclude thermosetting resins or photocurable resins, such as phenolresins, xylene resins, urea resins, melamine resins, benzoguanamineresins, benzoxazine resins, alkyd resins, triazine resins, furan resins,unsaturated polyesters, epoxy resins, silicon resins, polyurethaneresins, and polyimide resins; and thermoplastic resins, such aspolyvinyl alcohol, cellulose acetate resins, polypropylene resins,fluorine resins, phthalic acid resins, maleic acid resins, saturatedpolyesters, ethylene/vinyl alcohol copolymers, chitin, and chitosan.These polymeric compounds may be used alone or in the form of a mixtureof two or more thereof. The polymeric compound may be a copolymer or agraft polymer.

In a case where the porous layer is coated with the chemical-resistantpolymeric compound, the porous layer does not undergo a denaturation,such as dissolution or swelling to be deformed, at all when the porouslayer layered body contacts an intensely polar solvent, an alkali, anacid or some other chemical as described above. Alternatively, thedenaturation can be restrained to such a degree that a purpose of theuse, or the usage is not affected. For, for example, an article used insuch a manner that the period when the porous layer contacts chemicalsis short, it is necessary only to give the porous layer such a chemicalresistance that the porous layer is not denatured within the period.

In many cases, the chemical-resistant polymeric compound also has heatresistance. Thus, it is seldom feared that the porous layer is declinedin heat resistance. The coating with the chemical-resistant polymericcompound also makes it possible to change characteristics of the porouslayer surface. For example, the use of a fluorine resin also makes itpossible to make the surface water-repellent. The use of anethylene/vinyl alcohol copolymer also makes it possible to make thesurface hydrophilic. Furthermore, the use of a phenol resin also makesit possible to make the surface water-repellent to neutral water, andmake the surface hydrophilic to any aqueous alkaline solution. In such away, appropriate selection of the species of the polymeric compound usedfor the coating makes it possible to change the porous layer surface inaffinities (such as hydrophilicity) to a liquid.

Since the porous layer layered body of the present invention has theabove-mentioned structure, the layered body may be used for variousapplications in a wide range of fields. Specifically, in the state thatthe porous layer makes use of the pore properties which this layer hasas it is, the layered body may be used as a substrate material for thefollowing: for example, a low-permittivity material, a separator, acushion material, an ink-image receiving sheet, a test paper piece, anelectrically insulating material, a heat insulating material, or someother. Furthermore, the layered body may be used, in the form of afunctional laminate (composite material) wherein a different layer (suchas a metal plating layer or a magnetic plating layer) is layered overthe porous layer, for the following: for example, a substrate for acircuit, a heat radiating material (such as a heat sink or a heatradiating plate), an electromagnetic wave controlling material such asan electromagnetic wave shield or electromagnetic wave absorbent, anantenna, a cell culture substratum, or some other.

Next, a description is made about the functional laminate of the presentinvention. The functional laminate of the present invention is alaminate having the above-mentioned porous layer layered body, andhaving, over the surface of the porous layer of the layered body or apolymeric layer originating from the porous layer, a functional layerselected from the group consisting of an electroconductor layer, adielectric layer, a semiconductor layer, an electric insulator layer,and a resistor layer, wherein the porous layer or the polymeric layeroriginating from the porous layer has a crosslinked structure formedwith the crosslinking agent. This functional laminate may be called the“composite material” in the present specification.

The formation of the functional layer that may be of various types orthe precursor layer thereof onto the porous layer surface may beattained by, for example, a plating or printing technique.

The metal plating layer may be formed, for example, as a thin metalcoat, onto the porous layer surface. Examples of the metal whichconstitutes the metal plating layer include copper, nickel, silver,gold, tin, bismuth, zinc, aluminum, lead, chromium, iron, indium,cobalt, rhodium, platinum, and palladium; and alloys thereof. The metalcoat may be an alloy coat containing an element other than metals, whichmay be of various types. Examples of the alloy includenickel-phosphorus, nickel-copper-phosphorus, nickel-iron-phosphorus,nickel-tungsten-phosphorus, nickel-molybdenum-phosphorus,nickel-chromium-phosphorus, and nickel-boron-phosphorus. For the metalplating layer, the above-mentioned metals may be used alone or incombination of two or more thereof. The layer may be a single layer, ora laminate composed of plural layers.

The material which constitutes the magnetic plating layer is notparticularly limited as far as the material has magnetism. The materialmay be a ferromagnetic or paramagnetic material. Examples thereofinclude alloys, such as nickel-cobalt, cobalt-iron-phosphorus,cobalt-tungsten-phosphorus, and cobalt-nickel-manganese; and organicmagnetic materials, such as a methoxyacetonitrile polymer and any othercompound having a moiety from which a radical can be generated, a chargetransfer complex of decamethylferrocene and any other metal complexcompound, and polyacrylonitrile and any other compound that is asemi-graphitized carbon material.

For the formation of the metal plating layer, a known method, such aselectroless plating or electrolytic plating, may be used. In the presentinvention, electroless plating is preferably used since the porous layeris made of the polymer component(s). A combination of electrolessplating and electrolytic plating may be used.

As a plating solution used to form the metal plating layer, solutionshaving various compositions are known, and may be commercially availablefrom manufacturers. The composition of the plating solution is notparticularly limited, and it is advisable to select a compositionmatching with various desires (such as good appearance, hardness,abrasion resistance, discoloration resistance, corrosion resistance,electroconductivity, thermoconductivity, heat resistance, slidingperformance, water repellency, wettability, solder-wettability, sealingperformance, electromagnetic wave shielding property, and reflectivity).

An embodiment of the composite material-producing process of the presentinvention is performed by a method including the step of applying aphotosensitive composition made of a compound about which a reactivegroup is optically generated onto a surface of at least one porous layerthat constitutes the porous layer layered body of the present invention,thereby forming a photosensitive layer, the step of exposing thephotosensitive layer through a mask to light, thereby generatingreactive groups in the resultant exposed region, and the step of bondingthe reactive groups generated in the exposed region to a metal, therebyforming a conductor pattern; or a method including the step of using, inthe method described just above, a compound about which a reactive groupis optically lost instead of the optically-reactive-group-generatedcompound, and losing the reactive groups in a region exposed to light,and the step of bonding a portion of the reactive groups that remains inthe unexposed region to a metal, thereby forming a conductor pattern.

The optically-reactive-group-generated compound is not particularlylimited as far as the compound is a compound generating, in the moleculethereof, a reactive group which can form a bond to a metal, which may bea metal ion. Examples thereof include photosensitive compoundscontaining at least one derivative selected from onium salt derivatives,sulfonium ester derivatives, carboxylic acid derivatives, andnaphthoquinonediazide derivatives. These photosensitive compounds makeit possible to form an electroconductive region having a fine patternprecisely since the compounds are rich in versatility, and can easilygenerate a reactive group bondable to a metal by irradiation with light.

The optically-reactive-group-lost compound is, for example, a compoundthat has a reactive group that can not only form a bond to a metal,which may be a metal ion, but also comes not to be easily dissolved inwater or swelled therewith by a material that the reactive groupgenerates a hydrophobic functional group by irradiation with light.

The reactive group, which is optically generated or lost, is notparticularly limited as far as the group is a reactive group that canform a bond to a metal, which may be a metal ion. The group is, forexample, a functional group ion-exchangeable with a metal ion, and ispreferably a cation-exchangeable group. Examples of thecation-exchangeable group include acidic groups such as a —COOX group, a—SO₃X group, and a —PO₃X₂ group wherein Xs each represent a hydrogenatom, an alkali metal, an alkaline earth metal, or an ammonium group.Particularly preferred is a cation-exchangeable group having a pKa valueof 7.2 or less since this species can form bonds to a sufficient amountof a metal per unit area, so that the photosensitive layer can easilygain desired electroconductivity. Such a reactive group will beexchanged with a metal ion in the next step, so that the layer will beable to exhibit a stable adsorption ability based on a reduced body orfine particles of the metal.

The light to be radiated is not particularly limited as far as the lightcan promote the generation or loss of the reactive group. The light maybe, for example, light rays having wavelengths of 280 nm or more. Inorder to avoid deterioration of the porous layer layered body by thelight exposure, it is preferred to use light rays having wavelengths of300 nm or more (about 300 to 600 nm), in particular, light rays havingwavelengths of 350 nm or more.

After the irradiation through the mask with the light, the workpiece isoptionally washed, thereby making it possible to form a pattern made ofthe reactive groups in the exposed region or the unexposed region. Thethus-produced reactive groups produced in the porous layer surface arebonded to a metal by a method described below to form a conductorpattern.

In the present invention, the method for bonding the reactive groups tothe metal is preferably a method using electroless plating. It is knownthat electroless plating is generally useful as a method for laminatinga metal onto a resin layer made of plastic or the like. In order toimprove the adhesion between the porous layer surface and the metal, thesurface may be beforehand subjected to degreasing, washing, neutralizingor a catalyst treatment, or some other treatment. For the catalysttreatment, use may be made of, for example, a catalytic metal nucleusforming technique of causing a catalytic metal which can promote theprecipitation of a metal to adhere onto the surface to be treated.Examples of the catalytic metal nucleus forming technique include amethod of bringing the surface into contact with a colloidal solutioncontaining a catalytic metal (salt), followed by contact with an acid oralkali solution, or a reducing agent to promote chemical plating (acatalyzer-accelerator method); a method of bringing the surface intocontact with a colloidal solution containing fine particles of acatalytic metal, and then removing the solvent and additives by heatingor some other, to form catalytic metal nuclei (a metallic fine particlemethod); and a method of bringing the surface into contact with an acidor alkali solution containing a reducing agent, followed by contact withan acid or alkali solution of a catalytic metal to bring the surfaceinto contact with an activating liquid, thereby precipitating acatalytic metal (a sensitizing-activating method).

In the catalyzer-accelerator method, thecatalytic-metal-(salt)-containing solution may be, for example, atin-palladium mixed solution, or a solution containing a metal (salt)such as copper sulfate. In the catalyzer-accelerator method, forexample, the porous layer layered body is immersed in an aqueoussolution of copper sulfate, an excessive portion of copper sulfate isoptionally washed and removed, and next the workpiece is immersed in anaqueous solution of sodium borohydride, thereby making it possible toform catalytic nuclei of copper fine particles on the porous layersurface of the porous layer layered body. In the metallic fine particlemethod, for example, a colloidal solution wherein silver nanoparticlesare dispersed is brought into contact with the porous layer surface, andthen the workpiece is heated to remove the additives, such as thesurfactant or the binder, thereby making it possible to precipitatecatalytic nuclei made of the silver particles on the porous layersurface. In the sensitizing-activating method, for example, the surfaceis brought into contact with a solution of tin chloride in hydrochloricacid, followed by contact with a solution of palladium chloride inhydrochloric acid, thereby making it possible to precipitate catalyticnuclei made of palladium. The manner for bringing the porous layerlayered body into contact with any one of these treating liquids may be,for example, a manner of painting the liquid onto the porous layersurface on which a metal plating layer is to be layered, or a manner ofimmersing the porous layer layered body into the treating liquid.

In a case where in the catalytic metal nucleus forming technique, theporous layer layered body having two surfaces, one thereof being made ofits base and the other being made of its porous layer, is immersed inthe treating liquid, it is preferred that the base is made of ahomogenous layer. When the porous layer layered body, which has thesingle surface which the homogenous base constitutes, is immersed in thetreating liquid, catalytic nuclei are formed not only on the porouslayer surface of the porous layer layered body but also on the surfaceof the base; the catalytic nuclei adhere in a large amount onto theporous layer surface, which is large in surface area, and further thesurface easily holds the nuclei while the catalytic nuclei do notprecipitate easily on the homogenous base and further the nuclei easilydrop away since the base film surface is smooth. Thus, by subsequentelectroless plating, on the porous layer surface, on which the catalyticnuclei are formed in a sufficient amount, a metal plating layer will beable to be selectively formed.

Main examples of metal used in electroless plating include copper,nickel, silver, gold, and nickel-phosphorus. A plating solution used inelectroless plating contains, for example, the following componentsbesides the above-mentioned metals or salts thereof: a reducing agentsuch as formaldehyde, hydrazine, sodium hypophosphite, sodiumborohydride, ascorbic acid or glyoxylic acid, and a complexing agent orprecipitation controlling agent such as sodium acetate, EDTA, tartaricacid, malic acid, citric acid or glycine. Many of these components arecommercially available and can easily be obtained. The electrolessplating is performed by immersing, into the plating solution, the porouslayer layered body treated as described above. When the porous layerlayered body is subjected to electroless plating in the state that aprotective sheet is bonded onto a single surface of this porous layerlayered body, only the other surface undergoes the electroless plating.Thus, for example, the precipitation of the metal onto the base or someother can be prevented.

The thickness of the metal plating layer is not particularly limited,and may be appropriately selected in accordance with the usage. Thethickness is, for example, about 0.01 to 20 μm, preferably about 0.1 to10 μm. In order to make the thickness of the metal plating layer largeefficiently, performed is, for example, a method of combiningelectroless plating with electrolytic plating to form the metal platinglayer. In other words, by electroless plating, electroconductivity isgiven to the metal-coat-formed porous layer surface; thus, when thesurface is subsequently subjected to electrolytic plating, which isbetter in efficiency, a thick metal plating layer can be obtained in ashorter period.

The method is suitable particularly as a method for yielding a compositematerial used in a circuit substrate, a heat radiating material or anelectromagnetic wave controlling material.

Conventionally, circuit substrates are each generally formed by a methodof bonding a copper foil piece onto a surface of a substrate made ofglass/epoxy resin, polyimide or some other, and then removingunnecessary portions of the copper foil piece by etching to form wiring.However, according to such a conventional method, the formation of finewiring corresponding to circuit substrates about which the wiringdensity is being made higher has been becoming difficult. In order toadvance the technique of making wiring finer, it is necessary to cause avery thin copper foil piece to adhere strongly and closely onto asubstrate made of glass/epoxy resin, polyimide or some other; however,the thin copper foil piece is very poor in handleability, so that thestep of laminating the piece on the substrate is very difficult. Theproduction of the thin copper foil piece is difficult itself, and isexpensive. Furthermore, small is originally the adhesion force betweenglass/epoxy resin or polyimide, which is used as the raw material of thebase, and the copper foil piece, so that there is caused a problem thatwhen the technique of making wiring on any substrate finer is advanced,the wiring is peeled from the substrate.

Under such circumstances, the composite material of the presentinvention makes it possible to make fine openings in the porous layersurface of the porous layer layered body. Thus, in this case, asufficient adhesion force can be certainly kept between the surface anda metal plating layer thereon. The present invention is thereforesuitable as a material for a circuit substrate having fine wiring. Whenthe composite material constitutes a material for a circuit substrate,its metal plating layer is preferably made of copper, nickel, silver orsome other.

The porous layer layered body of the present invention is very useful asa circuit substrate produced by a method of forming fine wiring directlyonto a porous layer surface. As the process for producing this circuitsubstrate, use may be made of any process that has been described as theprocess for producing the composite material of the present invention.According to this process, the porous layer layered body of the presentinvention is used, so that fine wiring strongly entangled with theporous layer can be formed. Additionally, the wiring can easily beformed with good precision by a light exposure technique. When thelayered body is a film having, on a single surface thereof; a porouslayer, single-sided wiring can be formed. When the layered body is afilm having, on each surface thereof, a porous layer, double-sidedwiring can be formed. When via wiring, through which both surfaces areconnected to each other, is required, holes are made therein through aconventionally used drill or laser and the holes are filled or platedwith an electroconductive paste. In this way, the via wiring can beformed. Hitherto, known has been a technique of using electrolessplating to form wiring onto a porous body. However, porous bodies in theprior art have a problem of being small in strength to be poor inhandleability, and being broken in the process for producing the bodies.On the other hand, when the porous layer layered body of the presentinvention is used, its porous layer is shaped to adhere closely to itsbase; thus, the present invention can provide a circuit substrate whichcan certainly keep a sufficient strength and excellent handleability.

The electromagnetic wave controlling material is used, as a material forshielding or absorbing electromagnetic waves, to relieve or restrain aneffect produced onto a surrounding electromagnetic environment or aneffect received by an instrument itself from a surroundingelectromagnetic environment. Around us, there exist many electromagneticwave generators, such as electric/electronic instruments, wirelessinstruments, and systems, due to spread of digital electronicinstruments, personal computers and portable telephones. These radiatevarious electromagnetic waves. The electromagnetic waves radiated fromthese instruments may produce an effect onto a surroundingelectromagnetic environment, or the instruments themselves are alsoaffected from the surrounding electromagnetic environment. As measuresthereagainst, electromagnetic wave controlling materials, such as anelectromagnetic wave shield material or electromagnetic wave absorbentmaterial, have been becoming important year and year. According to thecomposite material of the present invention, for example, its metalplating layer gives electroconductivity to shield electromagnetic waves,whereby an electromagnetic wave shielding property can be imparted.Moreover, an electromagnetic wave absorbent material is filled into thepores in the porous layer, whereby an electromagnetic wave absorbingperformance can be imparted. Thus, the composite material is very usefulas an excellent electromagnetic wave controlling material.

The metal plating layer constituting the electromagnetic wavecontrolling material is preferably a layer that can giveelectroconductivity. It is effective that the layer is made of, forexample, nickel, copper or silver. When the composite material has alayer structure wherein a magnetic plating layer is formed on thesurface of the porous layer by electroless plating, the compositematerial is useful as an electromagnetic wave absorbent material. Thematerial used when the magnetic plating layer is formed by electrolessplating is, for example, a magnetic material such as nickel, or an alloymade of nickel-cobalt, cobalt-iron-phosphorus,cobalt-tungsten-phosphorus, or cobalt-nickel-manganese. About thecomposite material of the present invention, a very thin and flexiblematerial can be obtained, and the metal or magnetic material formed byplating is entangled with the porous layer; thus, the plating layer isnot easily peeled so that the composite material can be improved infolding endurance. The composite material can be used in the state ofbeing arranged at any place of an electronic instrument, or attachedthereto.

The porous layer layered body of the present invention is also useful asa low-permittivity material. By the advent of the broadband times, ithas become necessary to transmit a large volume of information at a highspeed. Thus, the frequency used for electronic instruments has been madehigh. Electronic instruments used under the situation need to cope withhigh frequency signals. When any conventional wiring board (made mainlyof glass epoxy resin) is used in a high frequency circuit, for example,the following problems are caused: (1) transmitted signals are delayedby a high permittivity; and (2) a high dielectric loss causes theinterference or attenuation of signals, an increase in powerconsumption, and heat inside the circuit. It is said that a porousmaterial is useful as a high-frequency wiring board material for solvingthese problems. This is because the porous material can attain a lowrelative permittivity thereof, while the relative permittivity of theair is as low as one. In the prior art, therefore, a porous substratematerial has been required. However, in order to make the permittivityof a substrate low, it is necessary to make the porosity thereof high.As a result, there arises a problem that the substrate is lowered instrength. In the porous layer layered body of the present invention, aporous layer is layered on a base so that the layered body has alow-permittivity property and further the porous layer adheres closelyonto the base; thus, the layered body can keep a strength sufficient forbeing handled, and is a medium preferred as a low-permittivity material.

When the porous layer layered body of the present invention is used as acircuit substrate material having a low permittivity, it is conceivablethat as described above, a wiring board is produced by a method ofbonding a copper foil piece onto the surface of the porous layer andthen etching an unnecessary portion of the copper foil piece to beremoved, thereby forming wiring. It has been becoming difficult to makewiring finer and make the density thereof higher. At present also,however, most circuit substrates are produced by this conventionalmethod. The porous layer layered body of the present invention may beused according to this method. Thus, it can be said that the porouslayer layered body is a useful material which can cope with a desirethat has been becoming very intense, that is, a desire that thepermittivity of the substrates is made low. In the case of using theporous layer layered body that is a layered body having fine pores lowin interconnection, an etchant does not easily enter the inside of theporous layer when its copper foil piece on the layered body is etched.Thus, it does not easily occur that the copper foil piece is unfavorablyetched from the rear side thereof. For this reason, good use can be madeof a characteristic of the porous layer low in interconnection, whichhas independent pores.

An embodiment of a process for producing the composite material of thepresent invention may be a process based on a printing technique. Sincethe porous layer layered body of the present invention is excellent inprintability, the layered body can be used in the state that a patternis formed on the porous layer by printing. In this way, the compositematerial is used as an ink-image receiving sheet (printing medium).Thus, the following describes a printing technique in detail.

Ink-image receiving sheets may be called printing media, and arefrequently used in a printing technique. At present, many printingprocesses are put into practical use. Examples of the printing techniqueinclude ink-jet printing, screen printing, dispenser printing,letterpress printing (flexography), sublimation type printing, offsetprinting, laser printer printing (toner printing), intaglio printing(gravure printing), contact printing, and micro-contact printing.Constituting components of an ink used therefor are not particularlylimited, and examples thereof include a conductor, a dielectric, asemiconductor, an insulator, a resistor, and a colorant.

Advantages obtained when an electronic material is produced by printingare, for example, as follows: (1) the material can be produced through asimple process, (2) the process is a low-load process to theenvironment, wherein the amount of wastes is small, (3) the material canbe produced in a short period with a low energy consumption, and (4)initial investment costs can be largely decreased. Actually, however, ahighly minute printing that has not been realized so far is required,and the printing is technically difficult. Accordingly, about printingused for producing electronic materials, printing results are largelyaffected by not only the performance of printing machines but alsoproperties of inks or ink-image receiving sheets. In the porous layerlayered body of the present invention, a porous layer adheres closely toa base, and a fine porous structure of the porous layer can adhereclosely to a printing plate without producing any gap because of thecushion performance thereof. Moreover, the layered body can absorb anink and fix the ink precisely, so that the layered body can attainhighly minute printing that has not been realized so far. Thus, thelayered body is very favorably used. Since the porous layer adheresclosely to the base, the layered body can ensure a strength sufficientfor being handled. For example, printing can be continuously madethereon in a roll-to-roll manner, so that the production efficiency canbe remarkably improved.

When an electronic material is produced by printing, the process for theprinting may be any one of the above-mentioned processes. Specificexamples of an electronic material produced by printing includeelectromagnetic wave controlling materials such as an electromagneticwave shield and an electromagnetic wave absorbent, a circuit substrate,an antenna, and a heat radiating plate. Examples of the material aremore specifically a liquid crystal display, an organic EL display, afield emission display (FED), an IC card, an IC tag, a solar battery, anLED element, an organic transistor, a condenser (capacitor), anelectronic paper, a flexible battery, a flexible sensor, a membraneswitch, a touch panel, and an EMI shield.

A process for producing the electronic material includes the step ofprinting, onto the surface of the porous layer (substrate), an inkcontaining an electronic material such as a conductor, a dielectric, asemiconductor, an insulator, or a resistor. For example, when a print ismade on the surface of the porous layer (substrate) with an inkcontaining a dielectric, a condenser (capacitor) can be formed. Examplesof the dielectric include barium titanate and strontium titanate. When aprint is made thereon with an ink containing a semiconductor, atransistor or some other can be formed. Examples of the semiconductorinclude pentacene, liquid silicon, a fluorene-bithiophene copolymer(F8T2), and poly(3-hexylthiophene) (P3HT).

When a print is made thereon with an ink containing a conductor, wiringcan be formed so that a flexible substrate, a TAB substrate, an antennaor some other can be produced. Examples of the conductor includeelectroconductive inorganic particles made of silver, gold, copper,nickel, ITO, carbon, and carbon nanotubes; and particles made ofelectroconductive organic polymers, such as polyaniline, polythiophene,polyacetylene and polypyrrole. Examples of the polythiophene includepoly(ethylenedioxythiophene) (PEDOT). These may be used in the form of asolution or a colloidal ink. Of these examples, preferred areelectroconductive particles that are inorganic particles. Particularlypreferred are silver particles or copper particles from the viewpoint ofbalance between electric properties and costs. Examples of the form ofthe particles include a spherical form and a scaly form (flake form).The particle size is not particularly limited, and the particles may beparticles in a scope from particles having an average particle diameterof several micrometers to the so-called nanoparticles, which have anaverage particle diameter of several nanometers. These particle speciesmay be used in the form of a mixture thereof. A description is made justbelow about the electroconductive ink, giving, as an example thereof, aneasily available silver ink (silver paste). However, the ink is notlimited thereto, and an ink of any other type may be used.

A silver ink generally contains, as constituents thereof, silverparticles, a surfactant, a binder, a solvent and others. In a differentembodiment, by use of a nature that silver oxide is heated to bereduced, an ink containing particles of silver oxide is printed and thenheated and reduced to be turned into silver wiring. In a furtherdifferent embodiment, an ink containing an organic silver compound isprinted, and then heated and decomposed to be turned into silver wiring.The organic silver compound may be a compound soluble in a solvent. Asthe particles which constitute the silver ink, silver particles, silveroxide, an organic silver compound, and others may be used alone or incombination. Particle species having different diameters may be used ina mixture form. The temperature (firing temperature) for curing thesilver ink after the ink is used to make a print may be appropriatelyselected in accordance with the composition of the ink, the particlediameter and others, and usually ranges from about 100 to 300° C. Sincethe porous layer layered body of the present invention is made of theorganic material(s), the firing temperature is preferably a relativelylow temperature to avoid deterioration thereof. In order to make theelectric resistance of wiring thereon small, it is generally preferredto fire the layered body at a high temperature. It is necessary toselect an ink having an appropriate curing temperature, and use the ink.Known examples of a commercially available product of the silver inkinclude inks “CA-2503” (trade name) manufactured by Daiken Chemical Co.,Ltd., “NANO DOTITE XA9053” (trade name) manufactured by Fujikura KaseiCo., Ltd., “NPS” and “NPS-J” (trade names) (having an average particlediameter of about 5 nm) manufactured by Harima Chemicals, Inc., and“FINE SPHERE SVW102” (trade name) (having an average particle diameterof about 30 nm) manufactured by Nippon Paint Co., Ltd. It is preferredto select the particle diameter, the particle diameter distribution, andthe blend proportion of a conductor or some other to be added to theink, considering balance between an electric resistance required for awiring board and the adhesion of the wiring.

In the case of screen printing, an ink is liable not to be held on ascreen if the viscosity thereof is too low. Thus, it is preferred thatthe viscosity is somewhat high. Even when the particle diameter of theparticles contained in the ink is large, no problem is caused. When theparticle diameter is small, it is preferred to decrease the amount ofthe solvent. It is therefore preferred that the particle diameter isabout 0.01 to 10 μm.

Wiring may be formed on only the single surface of the porous layer.When the porous layer is present on each of both surfaces of the base,the wiring may be formed on the surfaces. In the latter case, a via maybe optionally made for connecting both the surfaces to each other. Thevia hole may be formed with a drill or by a laser. The conductor insidethe via hole may be made of an electroconductive paste, or by plating.

The porous layer layered body may be used in the state that the surfaceof the wiring made of an electroconductive ink is coated with plating oran insulator. It is pointed out that silver wiring undergoeselectromigration or ion migration more easily, as compared with copperwiring (the 2002, June 17 issue of Nikkei Electronics, p. 75). Thus, itis effective to coat the surface of wiring made of a silver ink withplating in order to improve the reliability of the wiring. Examples ofthe plating include silver plating, gold plating, and nickel plating.The plating may be performed by a known method.

Furthermore, the porous layer layered body may be used in the state thatthe surface of the wiring made of an electroconductive ink is coatedwith a resin. This structure can be preferably used for the protectionor electrical insulation of the wiring, the prevention of the wiringfrom being oxidized or migrated, an improvement of the layered body inflexing property, and some other purpose. For example, it is feared thatsilver wiring and copper wiring are oxidized to be turned to silveroxide and copper oxide, respectively, thereby being lowered inelectroconductivity. However, the coating of the surface of such wiringwith the resin makes it possible to avoid the contact of oxygen or waterwith the wiring, thereby restraining a decline of the wiring inelectroconductivity. The method for coating the surface of the wiringselectively with the resin is, for example, a syringe, a dispenser,screen printing, or ink jetting, using a curable resin or soluble resinthat will be described later as the resin for the coating.

When the pores in the porous layer are kept after the formation of thewiring, the porous layer region is low in permittivity so that thelayered body is favorably used as a high-frequency wiring board.

About the manner of using the porous layer layered body of the presentinvention, the layered body is used in the state that the pores in theporous layer remain as they are. Moreover, the porous layer layered bodyof the present invention may be used in the state that the voidstructure of the porous layer is caused to disappear.

When the wiring surface is coated with a resin, the resin does noteasily invade the inside of the pores in a case where the porous layerhas independent fine pores, which are low in interconnection. Thus, thevoid structure tends to be maintained. Contrarily, if the porous layerhas fine pores having interconnection, the resin easily invades theinside of the pores so that the pore inside is filled with the resin.Thus, the void structure tends to disappear.

The resin for coating the wiring is not particularly limited, and is,for example, a curable resin usable with no solvent, or a soluble resinusable in the state of being dissolved in a solvent. When the solubleresin is used, it is necessary to perform the coating considering areduction in the volume when the solvent has vaporized.

Examples of the curable resin include an epoxy resin, an oxetane resin,an acrylic resin, and a vinyl ether resin.

The epoxy resin may be of various types, and examples thereof includebisphenol resins such as bisphenol A type and bisphenol F type resins,novolak resins such as phenol novolak and cresol novolak resins, andother glycidyl ether type epoxy resins; alicyclic epoxy resins; andmodified resins thereof. Usable examples of a commercially availableproduct of the epoxy resin include “ARALDITE” manufactured by HuntsmanAdvanced Materials, “DENACOL” manufactured by Nagase ChemteX Corp.,“CELLOXIDE” manufactured by Daicel Chemical Industries, Ltd., and“EPOTOHTO” manufactured by Tohto Kasei Co., Ltd. An epoxy resin curedproduct can be yielded by, for example, a method of: incorporating acuring agent into an epoxy resin to yield a curable resin composition;initiating, by effect of the composition, a curing reaction therein; andheating the system to promote the reaction. The curing agent for theepoxy resin may be, for example, an organic polyamine, an organic acid,an organic acid anhydride, a phenol, a polyamide resin, an isocyanate,or a dicyandiamide.

The epoxy resin cured product may also be yielded by a method ofincorporating a curing catalyst called a latent curing agent into anepoxy resin to yield a curable resin composition, and then heating thecomposition or irradiating the composition with light rays, such asultraviolet rays, to initiate a curing reaction therein. The latentcuring agent may be a commercially available product such as “SUNAID SI”manufactured by Sanshin Chemical Industry Co., Ltd.

In the case of using, as the epoxy resin cured product, a product highin flexibility, a flexible article such as a flexible substrate can beproduced. In the case of requiring an article to have heat resistance orhigh dimensional stability, the use of a composition that turns high inhardness after cured, as the curable resin composition, makes itpossible that the article is used as a rigid substrate (hard substrate).

In a case where the epoxy resin is used for the coating, the curableresin composition is high in handleability when low in viscosity.Examples of the composition having this feature include a bisphenol Ftype composition, and an aliphatic polyglycidyl ether type composition.

The oxetane resin is, for example, a product “ARON OXETANE” manufacturedby Toagosei Co., Ltd. An oxetane resin cured product can be yielded by amethod of mixing, for example, a cationic photopolymerization initiator“IRGACURE 250” manufactured by Ciba Specialty Chemicals Inc. with anoxetane resin, and then irradiating the mixture with ultraviolet rays toinitiate a curing reaction therein.

The soluble resin may be a commercially available product, such as alow-dielectric resin “OLIGO PHENYLENE ETHER” manufactured by MitsubishiGas Chemical Co., Inc., a polyamideimide resin “VYLOMAX” manufactured byToyobo Co., Ltd., a polyimide ink “UPICOAT” manufactured by UbeIndustries, Ltd., a polyimide ink “EVERLEC” manufactured by TohtoChemical Industry Co., Ltd., a polyimide ink “ULIN COAT” manufactured byNI Material Co., a polyimide ink “Q-PILON” manufactured by PI Research &Development Co., Ltd., and a saturated polyester resin “NICHIGOPOLYESTER”, an acrylic solvent type pressure-sensitive adhesive“CORPONIEL” and an ultraviolet/electron ray curable resin “SHIKOH” eachmanufactured by The Nippon Synthetic Chemical Industry Co., Ltd.

The solvent used at the coating time, wherein the soluble resin isdissolved, may be appropriately selected from known organic solvents inaccordance with the species of the resin. Typical examples of a resinsolution (soluble resin solution) wherein the soluble resin is dissolvedin a solvent include a resin solution wherein “OLIGO PHENYLENE ETHER” isdissolved in a versatile solvent such as methyl ethyl ketone or toluene;a resin solution wherein “VYLOMAX” is dissolved in a mixed solvent ofethanol and toluene (trade name: “HR15ET”); and a resin solution wherein“UPICOAT” is dissolved in triglyme.

The method for coating the wiring with the resin is not particularlylimited, and may be, for example, a method of using a syringe, a spoon,a dispenser, screen printing, ink jetting, or some other means todevelop (paint) the above-mentioned curable resin composition or solubleresin solution onto the porous layer surface and optionally removing anextra of the resin with a spatula or some other. The spatula may be, forexample, one made of polypropylene, a fluorine resin such as Teflon(registered trade name), a rubber such as silicone rubber, or a resinsuch as polyphenylene sulfide; or one made of a metal such as stainlesssteel. The spatula is in particular preferably one made of a resin sincethe wiring or the porous layer is not easily injured therewith. Themethod may be a method of using, without using any spatula, a meanscapable of controlling the jet amount, such as a syringe, a dispenser,screen printing or ink jetting, to drop out an appropriate amountthereof onto the porous layer surface.

In order to develop the resin smoothly onto the porous layer surface, aresin low in viscosity is preferably used as an uncured resin. About aresin high in viscosity, the resin is used in the state of being loweredin viscosity in a manner of being heated to an appropriate temperatureor some other manner, thereby making it possible to improve the resin inhandleability. However, in a case where a curable resin is used, thecuring reaction rate thereof is unfavorably raised when the resin isheated. Thus, heating more than required is not preferred since theheating makes the workability poor.

After the resin component is developed onto the porous layer surface, itis preferred to subject the workpiece to a heating treatment in order topromote the curing of the resin or volatilize the solvent. The methodfor the heating is not particularly limited. However, rapid heating maymake the resultant uneven since the resin or the curing agentvolatilizes, or the solvent volatilizes vigorously. Thus, the method ispreferably a method of raising the temperature mildly. Thetemperature-raising may be continuous or intermittent. It is preferredto adjust the temperature and the period for each of the curing and thedrying appropriately in accordance with the species of the resin or thesolvent.

The composite material of the present invention may be an embodimentwherein the void structure of the porous layer is maintained, or onewherein the void structure of the porous layer is caused to disappearafter the formation of the functional layer on the porous layer surface(after functionalization), so that the porous layer is preferably madetransparent.

According to the porous layer layered body of the present invention, ahighly minute print can be made on the porous layer by the poreproperties of the porous layer. However, the porous structure causesirregular reflection of visible rays, so that the porous layer iswhitened to be made opaque. Thus, when the layered body in this state isused as it is, the usage thereof is limited. Thus, a composition havinga glass transition temperature of 20° C. or higher is selected as thecomposition which constitutes the porous layer, whereby the voidstructure of the porous layer is lost through the heating treatment sothat irregular reflection is restrained. As a result, the porous layercan be made transparent.

The transparent porous layer is realized by the disappearance of thevoid structure inside the porous layer that is caused by heating theporous layer layered body, wherein a functional layer (pattern) that maybe of various types is formed on the porous layer surface, therebysoftening the porous layer slightly.

Accordingly, the present invention is also related to the followingaspects:

(13) A method of subjecting the layered body recited in any one of items(1) to (4) described above to a heating treatment at a temperature notlower than the glass transition temperature of the composition whichconstitutes the porous layer to cause the fine pores in the porous layerto disappear, thereby turning the porous layer to a transparent layer.

In this case, the porous-layer-constituting composition usually has aglass transition temperature of 20° C. or higher, and is softened ordeformed at a temperature that is not lower than the glass transitiontemperature (Tg) of the composition, lower than the heat-resistanttemperature of the base, and further lower than the decompositiontemperature of the porous-layer-constituting composition (containingpolymer(s) as a main component, a crosslinking agent, and optional othercomponents). Thus, although it depends on the species of the base, it ispreferred that the porous-layer-constituting composition has a glasstransition temperature of, for example, 280° C. or lower, in particular200° C. or lower, or 130° C. or lower.

The heating treatment for turning the porous layer to the transparentlayer can be conducted at a temperature that is not lower than the glasstransition temperature of the porous-layer-constituting composition,lower than the heat-resistant temperature of the base, and further lowerthan the decomposition temperature of the porous-layer-constitutingcomposition. In other words, the upper limit of the heating treatmenttemperature is lower than a lower temperature of the heat-resistanttemperature of the base, and the decomposition temperature of theporous-layer-constituting composition.

In order to conduct the heating treatment stably, the decompositiontemperature (decomposition starting temperature) of theporous-layer-constituting composition is required to be higher than theglass transition temperature of the porous-layer-constitutingcomposition by 15° C. or more, preferably by 30° C. or more, morepreferably by 50° C. or more. As this temperature difference is larger,the heating treatment can be more stably conducted. Thus, the upperlimit of this temperature difference is not decided. In general, mostpolymer components decompose in the range of higher temperatures thanthe glass transition temperature (Tg) thereof by 200° C. or more(Tg+200° C.); thus, the upper limit of this temperature difference maybe 200° C.

By the heating treatment, the porous-layer-constituting composition issoftened and deformed so that the fine pores disappear. Thus, the porouslayer is turned to a transparent layer. Without using any solvent, theporous layer is turned to the porous layer only by the heatingtreatment.

(14) A functional laminate, comprising a base, a transparent layercontaining a polymer as a main component on the base, and a functionallayer selected from the group consisting of an electroconductor layer, adielectric layer, a semiconductor layer, an electric insulator layer,and a resistor layer on the transparent layer, the functional laminatebeing obtained by performing:

the step of forming a layer selected from the group consisting of theelectroconductor layer, the dielectric layer, the semiconductor layer,the electric insulator layer, the resistor layer, and a precursor layerof these layers over the surface of the porous layer of the layered bodyrecited in any one of items (1) to (4) described above;

the step of subjecting the resultant layered body to a heating treatmentat a temperature not lower than the glass transition temperature of acomposition which constitutes the porous layer to cause the fine poresin the porous layer to disappear, thereby turning the porous layer to atransparent layer, and

the step of subjecting the workpiece to a heating treatment and/or anactive energy ray radiating treatment, thereby forming a crosslinkedstructure with the crosslinking agent in the porous layer.

The “transparent layer containing a polymer as a main component”referred to herein is a layer corresponding to the above-mentioned“polymeric layer originating from the porous layer”.

(15) The functional laminate according to item (14), wherein thefunctional layer is patterned.

(16) A process for producing a functional laminate comprising a base, atransparent layer containing a polymer as a main component on the base,and a functional layer selected from the group consisting of anelectroconductor layer, a dielectric layer, a semiconductor layer, anelectric insulator layer, and a resistor layer on the transparent layer,comprising:

the step of forming a layer selected from the group consisting of theelectroconductor layer, the dielectric layer, the semiconductor layer,the electric insulator layer and the resistor layer, and a precursorlayer of any one of the layers over the surface of the porous layer ofthe layered body recited in any one of items (1) to (4) described above;

the step of subjecting the resultant layered body to a heating treatmentat a temperature not lower than the glass transition temperature of acomposition which constitutes the porous layer to cause the fine poresin the porous layer to disappear, thereby turning the porous layer to atransparent layer, and

the step of subjecting the workpiece to a heating treatment and/or anactive energy ray radiating treatment, thereby forming a crosslinkedstructure with the crosslinking agent in the porous layer.

The precursor layer of any one of the layers means, for example, a layerthat can be turned to a conductor layer, a dielectric layer, asemiconductor layer, an electric insulator layer or a resistor layer bythe heating treatment or other treatment after this precursor layer isformed.

Depending on the conditions for the heating treatment in the step ofturning the porous layer to the transparent layer, the crosslinkingagent may react to form a crosslinked structure. In such a case, it isadvised to raise the temperature of the porous layer rapidly into atemperature range in which the porous layer softens, so as to completethe softening and the transparentization of the porous layer, andsubsequently cause the porous layer to react with the crosslinking agentto form a crosslinked structure. If the crosslinked structure would beformed on ahead, the porous layer would not be softened any more so thatthe porous structure would be kept.

(Conversely, when the porous structure is desired to be kept, it isadvisable to select the material to be used in such a manner that thesoftening temperature of the porous layer is made higher than thetemperature for the heating treatment for forming the crosslinkedstructure. When the heating crosslinking treatment is conducted at atemperature lower than the softening temperature of the porous layer,the porous structure is kept also after the formation of the crosslinkedstructure.)

(17) The functional laminate-producing process according to item (16)described above, wherein the functional layer is patterned.

When the porous-layer-constituting composition has a melting temperaturelower than the decomposition temperature thereof, it is preferred toconduct the above-mentioned heating treatment at a temperature lowerthan the melting temperature of the porous-layer-constitutingcomposition. If the heating treatment is conducted at the meltingtemperature or higher, the porous layer composition melts so that thefine pores are lost. Thus, the porous layer is turned to a transparentlayer. However, if the porous layer composition melts, the pattern ofthe patterned functional layer formed over the porous layer is unlikelyto be maintained.

In the case of selecting, as the base, a light-permeable base which hasa higher heat-resistant temperature than the glass transitiontemperature of the porous-layer-constituting composition, and haspractical heat resistance at a temperature permitting theporous-layer-constituting composition to soften or deform, a functionallaminate can be produced which has a transparent resin layer on thelight-permeable base, and a functional pattern printed on the resinlayer to be formed thereon. When the porous layer is transparentized inthis way, the resultant functional laminate can be used for variousmaterials for which light permeability is required, for example, amaterial for a display.

Herein, a description is made about the evaluation of thetransparentization in the conversion of the porous layer to thetransparent layer.

As shown by the equation described below, an index for the transparencyof the transparent layer converted from the porous layer can berepresented by the absolute value of the difference between the totallight transmittance (%) of the used base itself, and the total lighttransmittance (%) of the transparentized laminate (the base+thetransparent layer).

The transparency (T) of the transparent layer=|“the total lighttransmittance (Ts) of the base itself”−“the total light transmittance(Tst) of the laminate (the base+the transparent layer)”|

The reason why the absolute value of the difference between (Ts) and(Tst) is used in the equation is that the value (Tst) may be larger thanthe value (Ts). It appears that when fine irregularities are present inthe surface of the base itself, the presence of the transparent layer onthe surface causes the fine irregularities to be made flat and smooth torestrain irregular reflection, thereby making the value (Tst) largerthan the value (Ts).

Considering a case where the present invention is used for anapplication for which transparentization is required, the value of thetransparency (T) of the transparent layer is, for example, 0 to 30%,preferably 0 to 20%, more preferably 0 to 10%, in particular preferably0 to 5%. If the transparency (T) of the transparent layer would be morethan 30%, the conversion of the porous layer to the transparent layerwould be insufficient. In the evaluation of the transparentization, itis necessary to measure the total light transmittance (%) of thelaminate (the base+the transparent layer) at its region where nofunctional layer such as a conductor layer is formed. The functionallayer generally inhibits the permeation of light rays. The total lighttransmittance may be measured by use of a haze meter, NDH-5000W,manufactured by Nippon Denshoku Industries Co., Ltd. in accordance withJIS K7136.

The thickness of the obtained transparent layer is calculated out on thebasis of the thickness and the porosity of the porous layer.

The thickness of the transparent layer=“the thickness of the porouslayer”×(100−the porosity)/100

In the present invention, the thickness of the porous layer is 0.1 to100 μm, and the porosity is 30 to 85%; thus, the thickness of thetransparent layer may range from 0.015 to 70 μm. Referring to theabove-mentioned respective preferred ranges of the thickness and theporosity of the porous layer, it is advisable to decide a desiredthickness of the transparent layer appropriately.

When the transparentized resin layer originating from the porous layeris used in, for example, a wiring board, the wiring can easily beinspected. Moreover, when the wiring board is integrated into a device,the relationship between positions of its parts is easily recognizable.By these matters and others, the wiring board is favorably very good inhandleability. Furthermore, it is preferred that the base of the porouslayer layered body is high in transparency.

The base of the porous layer layered body used in the present inventionis preferable since the base has such heat resistance that the base isnot deformed at a heating treatment temperature for transparentizing theporous layer. If the base is deformed, the base is lowered indimensional stability for a wiring substrate.

The upper limit temperature of the heating treatment fortransparentizing the porous layer is varied in accordance with the base,and is not specified without reservation. When a polyimide is used forthe base, the heating temperature is appropriately 400° C. or lower,preferably 300° C. or lower, in particular preferably 260° C. or lower.The heating treatment period depends on the components which constitutethe porous layer, and is not specified without reservation, either. Theperiod is appropriately 1 minute to 3 hours, preferably about 3 minutesto 1 hour. The heating may be conducted at a single stage or two stages.In the case of using a functional material that can be fired at a lowtemperature, such as silver ink, it is allowable to print the ink, firethe ink, and then raise the temperature of the workpiece totransparentize the porous layer, or to set the temperature of theworkpiece to a temperature applicable to both of the firing of the inkand the transparentizing treatment, and attain the two at a singlestage.

When the transparentization of the porous layer is attained by a heatingtreatment, the porous-layer-constituting composition needs to have aglass transition temperature of 20° C. or higher. If the glasstransition temperature is lower than 20° C., the porous structure may beunfavorably changed even at room temperature.

The above-mentioned International Publication WO2007/097249 disclosesthat a porous layer layered body on which wiring is formed is wettedwith a solvent to swell and soften the porous layer, thereby causing thevoid structure in the porous layer to disappear (paragraphs [0228] to[0232]), to transparentize the porous layer. However, after the swellingand softening of the porous layer, it is necessary to conduct a solventdrying treatment. Thus, the successive steps are complicated so thatproduction costs increase. If the solubility of the porous layer in theused solvent is high, the porous layer itself is unfavorably dissolvedso that the wiring pattern formed on the porous layer is not easilymaintained. From this viewpoint, it is largely advantageous that theporous layer is turned to a transparent layer only by a heatingtreatment without using any solvent.

In the meantime, electromagnetic waves are generated from displays suchas a PDP to produce a bad effect (noise) onto peripheral instruments. Inorder to prevent (shield) such electromagnetic waves, it is necessary togive an electromagnetic wave shielding function to a filter to bearranged on the front surface of a PDP. As the filter, a film on whichwiring is laid into a lattice form is used.

Electromagnetic wave shield films having the above-mentioned use purposegenerally have a structure wherein a metallic layer is layered on a filmhaving high transparency (highly transparent film). The films can eachbe formed by, for example, a method of laying the metallic layer ontothe highly transparent film by sputtering, or a method of bonding acopper foil piece or the like onto the highly transparent film and thenetching the workpiece to make a metallic mesh. An example of theelectromagnetic wave shield film is a film having a lattice patternhaving a line width of 20 to 30 μm and a pitch (recurring interval) ofabout 300 μm.

According to the present invention, an electromagnetic wave shield filmhaving the above-mentioned structure can be provided by forming wiringin a lattice form onto the porous layer layered body and then subjectingthe workpiece to a transparentizing treatment. At this time, costs wouldbe able to be decreased by forming the wiring simply, for example, inthe manner that the wiring is provided using a printing method, such asscreen printing.

Furthermore, the transparency of the wiring region can be made high byattaining the printing using ITO (indium tin oxide), which is atransparent (transmittance to visible rays: about 90%) conductor. Usemay be made of, for example, an ITO ink manufactured by C.I. Kasei Co.,Ltd., or an ITO ink “NANO METAL INK” manufactured by ULVAC Materials,Inc. The use of the transparent conductor may make it possible that theporous layer layered body is used as a flat panel display, such as aliquid crystal panel or an organic EL, a solar battery, a resistivetouch panel, or some other. It is allowable to use a method of formingthe wiring by use of a zinc oxide ink as another transparent conductor.

The composite material of the present invention may have a structurewherein the pores in the porous layer remain as they are. The compositematerial wherein the pores in the porous layer remain as they are meanthat the porous layer has properties acting as a porous body.Specifically, it means, for example, that the composite material keeps avoid structure equivalent to that of the porous layer when its conductoris formed by a printing technique. Such a composite material may have astructure wherein a different layer is layered, or a structure subjectedto a treatment that may be of various types as far as the porous layercan hold properties acting as a porous body.

For example, when the pores in the porous layer are left as they are inorder that the layered body can attain, for example, a low permittivity,the layered body is not subjected to any solvent treatment. However,only its wiring region may be coated with a resin by any one of themethods exemplified above to protect the wiring, insulate the wiring,prevent the oxidization of the wiring, and improve the layered body inflexing property.

As has been described about the resin-filling into the porous layer, thecomposite material can be made better in transparency when its wiring isformed by use of an ink of ITO or zinc oxide, which is a transparentconductor. The use of the composite material can be developed intoarticles for which such a property is required. By the above-mentionedmethod, the porous structure can be caused to disappear to make theporous layer transparent; however, in this case, the wiring thereon maybe naked. It is preferred to coat the wiring with a resin as has beendescribed hereinbefore, or form a coverlay thereon to insulate thewiring certainly from the others.

Usually, wiring boards are each joined to other parts or a substratethrough solder, a connector or some other to cause electricity to flowinto the board. Thus, the joint region needs to be filled with a resinin the state of being masked, or these members need to be coated with aresin except the joint region. This resin, that is, the resin forcoating the wiring may be a curable resin or soluble resin, examples ofwhich have been described above.

Wiring boards are not each composed of only wiring. Semiconductor chips,such as a TAB or COF, condensers, resistors and others can be joinedonto the wiring board through solder, wire bonding, or some other.Furthermore, the formation of wiring or the mounting of parts may beapplied to a single surface of the porous layer layered body, or to bothsurfaces thereof. Wiring boards may be stacked onto each other to make amultilayered wiring board.

In the composite material of the present invention, a coverlay may belayered on the porous layer. In the case of, for example, a flexiblesubstrate, its wiring is generally coated with a coverlay made of aresin film such as a polyimide film or PET film to protect the wiring,insulate the wiring, prevent the oxidization of the wiring, and improvethe composite material in flexing property. Examples of a film for thecoverlay include “NIKAFLEX” manufactured by Nikkan Industries Co., Ltd.,and products manufactured by Arisawa Manufacturing Co., Ltd.

The method for laminating the coverlay is, for example, a method ofpressure-bonding, with heat, a coverlay film wherein an adhesive ispainted on a single surface of a coverlay, such as a polyimide film orPET film, onto the porous layer after the layer is subjected to asolvent treatment. The adhesive of the coverlay film may be a knownadhesive. The adhesive is in a semi-cured state (B stage) in many casesto be easily handled.

The coverlay is not necessarily required and may be omitted when onlythe coating of the wiring on the porous layer with the resin makes itpossible to attain sufficiently the protection and the insulation of thewiring, the prevention thereof from being oxidized, and the maintenancein flexing property.

The porous layer layered body of the present invention may be used foran antenna better in high frequency property.

Recently, many wireless instruments have been used, and antennas havebeen needed to transmit and receive signals. Portable telephones,wireless LANs and IC cards have been remarkably spreading. The use of anantenna made of a low-permittivity material is preferred since the usecan increase the gain of the antenna. For example, for IC cards andothers, loop-form RFID antennas are used. At present, these antennas areproduced by a subtractive technique (etching technique).

When a PET substrate or the like that has been used so far is replacedby the porous layer layered body of the present invention, an antennabetter in high frequency property can be produced. A production processthereof may be according to the subtracting technique. Specifically, inthe same manner as described about the process for producing alow-permittivity circuit substrate, the antenna-producing process may bea process of bonding a copper foil piece onto the surface of the porouslayer layered body wherein its base is a resin film, or a surface of aporous film to form a resist pattern, and then removing an unnecessaryportion of the copper foil piece by etching. Another example of theantenna-producing process may be a process of forming a resist patternonto the porous layer layered body wherein its base is a metal foilpiece of copper or some other metal, and then etching an unnecessaryportion of the copper foil piece to be removed. The subtractivetechnique that has been conventionally performed has a long process torequire much labor and cost. In the same manner as described about theink-image receiving sheet, the antenna can be more simply produced atlow costs by using a method of printing an ink containing a conductor toform the antenna.

JP-A-2006-237322 discloses a process for producing a copper polyimidesubstrate. The process is a process of making a surface of a polyimideresin film hydrophilic to form a physical development nuclei layer,forming a silver film thereon by a silver diffusion transfer process,and then plating the workpiece with copper.

Since any polyimide resin film is poor in bondability, the surfacethereof needs to be subjected to an alkali treatment or a coronadischarge treatment in order to modify the surface. However, in theporous layer layered body of the present invention, a porous layerhaving many fine pores can be formed on a polyimide resin film.Therefore, an adhesive layer thereon can enter the inside of the poresso that a more intense adhesion can be expected therebetween by ananchor effect thereof. Thus, the porous layer layered body can befavorably used for the above-mentioned purposes.

EXAMPLES

Hereinafter, the present invention will be described in more detail byway of working examples; however, the present invention is not limitedto these working examples. First, individual measuring methods will bedescribed.

The average pore diameter and the porosity of any porous layer werecalculated out by methods described below. The average pore diameter andthe porosity were gained, using only fine pores viewed in an electronmicroscopic photograph as objects.

1. Average Pore Diameter

About 30 or more pores were selected at will in a surface or a crosssection of any layered body, and the respective areas thereof weremeasured from an electron microscopic photograph thereof. The averagevalue thereof was defined as the average pore area Save. It waspresupposed that the pores were true circles. The following equation wasused to convert the pore diameter from the average pore area, and theresultant value was defined as the average pore diameter:

the average pore diameter [μm] in the surface or theinside=2×(Save/π)^(1/2)

wherein π represents the circular constant.

2. Porosity

The porosity of the inside of the porous layer was calculated out inaccordance with the following equation:

the porosity [%]=100−100×W/(ρ·V)

wherein V represents the volume [cm³] of the porous layer; W, the weight[g] of the porous layer; and ρ, the density [g/cm³] of the compositionof the porous layer (the density of the porous layer composition iscalculated out by distributing the densities of the individualcomponents constituting the composition in accordance with their ratiosby weight in the composition). The volume V and the weight W of theporous layer were calculated out by subtracting, from the volume and theweight of the laminate wherein the porous layer was layered on the base,the volume and the weight of the base, respectively.

In porous layer compositions, the density of each of the components isas follows:

the density of a polyamideimide, VYLOMAX N-100H: 1.45 [g/cm³],

that of a polyimide, Pyre-M. L. RC5019: 1.43 [g/cm³],

that of an epoxy resin, YDCN-700-5: 1.21 [g/cm³],

that of an epoxy resin, jER 828: 1.17 [g/cm³],

that of an epoxy resin, jER 834: 1.18 [g/cm³],

that of an epoxy resin, jER 1001: 1.19 [g/cm³],

that of an epoxy resin, jER 1004: 1.19 [g/cm³], and

that of an epoxy resin, jER 152: 1.21 [g/cm³].

3. Tape Peeling Test

The interlayer adhesion between a base and a porous layer of any layeredbody in an uncrosslinked state was measured by the following tapepeeling test:

(i) A masking tape “FILM MASKING TAPE No. 603 (#25)” manufactured byTeraoka Seisakusho Co., Ltd., having a width of 24 mm, is attached ontothe surface of the porous layer of the layered body over a length of 50mm from an end of the tape. The attached tape is pressure-bonded thereonwith a roller (oil-resistant hard rubber roller No. 10, manufactured byHolbein Art Material Inc.) having a diameter of 30 mm and giving a loadof 200 gf.(ii) A universal tensile tester [trade name: “TENSILON RTA-500”,manufactured by Orientic Co., Ltd.] is used to pull the other end of thetape at a peel rate of 50 min/minute, thereby peeling the tape into aT-shape.(iii) It is observed whether or not interfacial peeling is causedbetween the porous layer and the base.

4. Adhesion Evaluating Test (Cross-Cut Method)

The interlayer adhesion between a base and a porous layer of any layeredbody before and after the layered body was subjected to a heatingcrosslinking treatment was measured in accordance with an adhesionevaluating test (cross-cut method) according to JIS K 5600-5-6.

In a sample thereof, cross-cut lines having a cut interval of 2 mm wereformed to make this test. A transparent pressure-sensitive adhesive tapeused therefor was Cellotape (registered trade name) NO. 405 manufacturedby Nichiban Co., Ltd. and having a width of 24 mm (adhesion force: 4.00N/10 mm). An evaluation made after the tape was peeled was also inaccordance with JIS K 5600-5-6.

Evaluation classification (an outline thereof is described. Detailsthereof are described in JIS K 5600-5-6):

0: No peeling is caused in any one of the squares.

1: The percentage of an area affected in the cross-cut region is clearly5% or less.

2: The percentage of an area affected in the cross-cut region is clearlymore than 5%, but is 15% or less.

3: The percentage of an area affected in the cross-cut region is clearlymore than 15%, but is 35% or less.

4: The percentage of an area affected in the cross-cut region is clearlymore than 35%, but is 65% or less.

5: The degree of the peeling is over that classified into the class 4.

Chemical Resistance Evaluating Test (Solubility of a Porous Layer inNMP)

About a porous layer of any layered body before and after the layeredbody was subjected to a heating crosslinking treatment, a chemicalresistance test was made as follows.

A sample of the layered body was cut into a piece having a size of about40 mm×30 mm, and a syringe was used to drop out, on the porous layerthereof, one drop (about 26 mg) of N-methyl-2-pyrrolidone (NMP). After 2minutes, the sample was immersed in a large volume (about 1 liter) ofwater, and then the water was stirred to wash away NMP. Thereafter, thesample was taken out, and naturally dried on a waste cloth at roomtemperature. After the drying, the state of the sample was observed withthe naked eye.

Example 1 Porous Layer Layered Body A

The following were mixed with each other: a polyamideimide resinsolution (trade name: “VYLOMAX N-100H” manufactured by Toyobo Co., Ltd.;solid content concentration: 20% by weight; solvent: NMP(N-methyl-2-pyrrolidone); solution viscosity: 350 dPa·s/25° C.); anovolak type epoxy resin (trade name: “YDCN-700-5”, manufactured byTohto Kasei Co., Ltd.) as a crosslinking agent; and NMP as a solvent.The blend ratio of the polyamideimide resin/NMP/the novolak type epoxyresin was a ratio by weight of 15/85/5. In this way, a film-formingmaterial solution was obtained. A polyimide film (trade name: “KAPTON200H” manufactured by Du Pont-Toray Co., Ltd.; thickness: 50 μm) as abase was fixed on a glass plate with a tape. A film applicator was usedto cast the material solution, the temperature of which was set to 25°C., thereon under a condition that the gap between the film applicatorand the base was 51 μm. After the casting, the workpiece was rapidly putinto a container having a humidity of about 100% and a temperature of50° C., and then kept for 4 minutes. Thereafter, the workpiece wasimmersed in water to coagulate the cast solution. Next, without peelingthe coagulated matter from the base, the workpiece was naturally driedat room temperature to yield a layered body A wherein a porous layer waslayered on the base. The thickness of the porous layer was about 10 μm,and the total thickness of the layered body was about 60 μm.

About the resultant layered body A, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body A was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.5 μm.The porosity of the inside of the porous layer was 80%.

Example 2 Porous Layer Layered Body B

A layered body B wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the novolak type epoxy resin with each other to set theratio by weight of the polyamideimide resin/NMP/the novolak type epoxyresin to 15/85/10. The thickness of the resultant porous layer was about11 μm, and the total thickness of the layered body was about 61 μm.

About the resultant layered body B, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body B was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.3 μm.The porosity of the inside of the porous layer was 77%.

Example 3 Porous Layer Layered Body C

A layered body C wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the novolak type epoxy resin with each other to set theratio by weight of the polyamideimide resin/NMP/the novolak type epoxyresin to 15/85/15. The thickness of the resultant porous layer was about21 μm, and the total thickness of the layered body was about 71 μm.

About the resultant layered body C, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body C was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.5 μm.The porosity of the inside of the porous layer was 75%.

Comparative Example 1 Porous Layer Layered Body D

A layered body D wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that afilm-forming material solution was yielded by mixing the polyamideimideresin and NMP with each other to set the ratio by weight of thepolyamideimide resin/NMP to 15/85 without adding any crosslinking agentto the film-forming material solution. The thickness of the resultantporous layer was about 15 μm, and the total thickness of the layeredbody was about 65 μm.

About the resultant layered body D, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body D was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.5 μm.The porosity of the inside of the porous layer was 82%.

Example 4 Porous Layer Layered Body E

A layered body E wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that abisphenol A type epoxy resin (trade name: “jER 828”, manufactured byJapan Epoxy Resins Co., Ltd.) was used as a crosslinking agent, and afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the bisphenol A type epoxy resin with each other to setthe ratio by weight of the polyamideimide resin/NMP/the bisphenol A typeepoxy resin to 20/80/10. The thickness of the resultant porous layer wasabout 23 μm, and the total thickness of the layered body was about 73μm.

About the resultant layered body E, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body E was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.5 μm.The porosity of the inside of the porous layer was 72%.

Example 5 Porous Layer Layered Body F

A layered body F wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that abisphenol A type epoxy resin (trade name: “jER 834”, manufactured byJapan Epoxy Resins Co., Ltd.) was used as a crosslinking agent, and thefilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the bisphenol A type epoxy resin with each other to setthe ratio by weight of the polyamideimide resin/NMP/the bisphenol A typeepoxy resin to 20/80/10. The thickness of the resultant porous layer wasabout 29 μm, and the total thickness of the layered body was about 79μm.

About the resultant layered body F, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body F was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 2.0 μm.The porosity of the inside of the porous layer was 72%. In FIG. 1 isshown an electron microscopic photograph (power:×5000) of the porouslayer surface, and in FIG. 2 is shown an electron microscopic photograph(power: ×2000) of a cross section of the layered body.

Example 6 Porous Layer Layered Body G

A layered body G wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that abisphenol A type epoxy resin (trade name “jER 1001”, manufactured byJapan Epoxy Resins Co., Ltd.) was used as a crosslinking agent, and afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the bisphenol A type epoxy resin with each other to setthe ratio by weight of the polyamideimide resin/NMP/the bisphenol A typeepoxy resin to 20/80/10. The thickness of the resultant porous layer wasabout 34 μm, and the total thickness of the layered body was about 84μm.

About the resultant layered body G, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body G was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.8 μm.The porosity of the inside of the porous layer was 70%.

Example 7 Porous Layer Layered Body H

A layered body H wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that abisphenol A type epoxy resin (trade name: “jER 1004”, manufactured byJapan Epoxy Resins Co., Ltd.) was used as a crosslinking agent, and afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the bisphenol A type epoxy resin with each other to setthe ratio by weight of the polyamideimide resin/NMP/the bisphenol A typeepoxy resin to 20/80/10. The thickness of the resultant porous layer wasabout 30 μm, and the total thickness of the layered body was about 80μm.

About the resultant layered body H, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body H was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.8 μm.The porosity of the inside of the porous layer was 71%.

Example 8 Porous Layer Layered Body I

A layered body I wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that aphenol novolak type epoxy resin (trade name: “jER 152”, manufactured byJapan Epoxy Resins Co., Ltd.) was used as a crosslinking agent, and afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the phenol novolak type epoxy resin with each other toset the ratio by weight of the polyamideimide resin/NMP/the phenolnovolak type epoxy resin to 20/80/10. The thickness of the resultantporous layer was about 31 μm, and the total thickness of the layeredbody was about 81 μm.

About the resultant layered body I, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body I was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.5 μm.The porosity of the inside of the porous layer was 72%.

Comparative Example 2 Porous Layer Layered Body J

A layered body J wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 1 except that apolyamideimide resin solution (trade name: “VYLOMAX N-100H” manufacturedby Toyobo Co., Ltd.; solid content concentration: 20% by weight;solvent: NMP; solution viscosity: 350 dPa·s/25° C.) was used, as it was,as a film-forming material solution without adding any crosslinkingagent to the film-forming material solution. The thickness of theresultant porous layer was about 14 μm, and the total thickness of thelayered body was about 64 μm. In other words, in the film-formingmaterial solution, the ratio by weight of the polyamideimide resin toNMP was 20/80.

About the resultant layered body J, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body J was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and a skin layer was basically formed on the surface ofthe porous layer. Throughout the inside of the porous layer, there wereindependent and substantially homogeneous fine pores having an averagepore diameter of about 1.2 μm. The porosity of the inside of the porouslayer was 77%.

Example 9 Porous Layer Layered Body K

The following were mixed with each other: a polyamideimide resin (tradename: “TORLON AI-10” manufactured by Solvay Advanced Polymers); NMP as asolvent; and a bisphenol A type epoxy resin (trade name: “jER 828”,manufactured by Japan Epoxy Resins Co., Ltd.) as a crosslinking agent.The blend ratio of the polyamideimide resin/NMP/the bisphenol A typeepoxy resin was a ratio by weight of 25/75/5. In this way, afilm-forming material solution was obtained. A polyimide film (tradename: “KAPTON 200H” manufactured by Du Pont-Toray Co., Ltd.; thickness:50 μm) as a base was fixed on a glass plate with a tape. A filmapplicator was used to cast the material solution, the temperature ofwhich was set to 25° C., thereon under a condition that the gap betweenthe film applicator and the base was 25 μm. After the casting, theworkpiece was rapidly put into a container having a humidity of about100% and a temperature of 50° C., and then kept for 4 minutes.Thereafter, the workpiece was immersed in water to coagulate the castsolution. Next, without peeling the coagulated matter from the base, theworkpiece was naturally dried at room temperature to yield a layeredbody K wherein a porous layer was layered on the base. The thickness ofthe porous layer was about 20 μm, and the total thickness of the layeredbody was about 70 μm.

About the resultant layered body K, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body K was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.7 μm.The porosity of the inside of the porous layer was 74%.

Example 10 Porous Layer Layered Body L

A layered body L wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 9 except that aphenol novolak type epoxy resin (trade name: “jER 152”, manufactured byJapan Epoxy Resins Co., Ltd.) was used as a crosslinking agent, and afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP and the phenol novolak type epoxy resin with each other toset the ratio by weight of the polyamideimide resin/NMP/the phenolnovolak type epoxy resin to 25/75/5. The thickness of the resultantporous layer was about 18 μm, and the total thickness of the layeredbody was about 68 μm.

About the resultant layered body L, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body L was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.7 μm.The porosity of the inside of the porous layer was 72%.

Comparative Example 3 Porous Layer Layered Body M

A layered body M wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 9 except that afilm-forming material solution was yielded by mixing the polyamideimideresin and NMP with each other to set the ratio by weight of thepolyamideimide resin/NMP to 25/75 without adding any crosslinking agentto the film-forming material solution. The thickness of the resultantporous layer was about 20 μm, and the total thickness of the layeredbody was about 70 μm.

About the resultant layered body M, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body M was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.7 μm.The porosity of the inside of the porous layer was 76%.

Example 11 Porous Layer Layered Body N

The following were mixed with each other: a polyimide resin solution(trade name: “Pyre-M. L. RC5019” manufactured by I. S. T. Co.; solidcontent concentration: 15.7% by weight; solvent: NMP; solutionviscosity: 69.1 dPa·s/25° C.); and a bisphenol A type epoxy resin (tradename: “jER 828”, manufactured by Japan Epoxy Resins Co., Ltd.) as acrosslinking agent. The blend ratio of the polyimide resin/NMP/thebisphenol A type epoxy resin was a ratio by weight of 15.7/84.3/10. Inthis way, a film-forming material solution was obtained. A polyimidefilm (trade name: “KAPTON 200H” manufactured by Du Pont-Toray Co., Ltd.;thickness: 50 μm) as a base was fixed on a glass plate with a tape. Afilm applicator was used to cast the material solution, the temperatureof which was set to 25° C., thereon under a condition that the gapbetween the film applicator and the base was 51 μm. After the casting,the workpiece was rapidly put into a container having a humidity ofabout 100% and a temperature of 50° C., and then kept for 4 minutes.Thereafter, the workpiece was immersed in water to coagulate the castsolution. Next, without peeling the coagulated matter from the base, theworkpiece was naturally dried at room temperature to yield a layeredbody N wherein a porous layer was layered on the base. The thickness ofthe porous layer was about 35 μm, and the total thickness of the layeredbody was about 85 μm.

About the resultant layered body N, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body N was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 3.0 μm.The porosity of the inside of the porous layer was 63%.

Comparative Example 4 Porous Layer Layered Body O

A layered body O wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 11 except that apolyimide resin solution (trade name: “Pyre-M. L. RC5019” manufacturedby I. S. T. Co.; solid content concentration: 15.7% by weight; solvent:NMP; solution viscosity: 69.1 dPa·s/25° C.) was used, as it was, as afilm-forming material solution without adding any crosslinking agent tothe film-forming material solution. The thickness of the resultantporous layer was about 17 μm, and the total thickness of the layeredbody was about 67 μm. In other words, in the film-forming materialsolution, the ratio by weight of the polyimide resin to NMP was15.7/84.3.

About the resultant layered body O, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body O was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 5.0 μm.The porosity of the inside of the porous layer was 65%.

Example 12 Porous Layer Layered Body P

A layered body P wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 4 except that thefollowing was used instead of the polyimide film (trade name: “KAPTON200H” manufactured by Du Pont-Toray Co., Ltd.; thickness: 50 μm) as thebase: a surface-treated rolled copper foil piece (trade name:“RCF-T5B-18”, manufactured by Fukuda Metal Foil & Powder Co., Ltd.;thickness: 18 μm). The thickness of the resultant porous layer was about32 μm, and the total thickness of the layered body was about 50 μm.

About the resultant layered body P, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body P was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and recognized was a tendency that a skin layer wasbasically formed on the surface of the porous layer. Throughout theinside of the porous layer, there were independent and substantiallyhomogeneous fine pores having an average pore diameter of about 1.5 μm.The porosity of the inside of the porous layer was 70%.

Example 13 Porous Layer Layered Body Q

The following were mixed with each other: a polyamideimide resinsolution (trade name: “VYLOMAX N-100H” manufactured by Toyobo Co., Ltd.;solid content concentration: 20% by weight; solvent: NMP; solutionviscosity: 350 dPa·s/25° C.); NMP as a solvent; polyvinyl pyrrolidone(molecular weight: 50000) as a water-soluble polymer; and a bisphenol Atype epoxy resin (trade name: “jER 828”, manufactured by Japan EpoxyResins Co., Ltd.) as a crosslinking agent. The blend ratio of thepolyamideimide resin/NMP/polyvinyl pyrrolidone/the bisphenol A typeepoxy resin was a ratio by weight of 15/85/25/15. In this way, afilm-forming material solution was obtained. A polyimide film (tradename: “KAPTON 200H” manufactured by Du Pont-Toray Co., Ltd.; thickness:50 μm) as a base was fixed on a glass plate with a tape. A filmapplicator was used to cast the material solution, the temperature ofwhich was set to 25° C., thereon under a condition that the gap betweenthe film applicator and the base was 51 μm. After the casting, theworkpiece was rapidly put into a container having a humidity of about100% and a temperature of 50° C., and then kept for 4 minutes.Thereafter, the workpiece was immersed in water to coagulate the castsolution. Next, without peeling the coagulated matter from the base, theworkpiece was naturally dried at room temperature to yield a layeredbody Q wherein a porous layer was layered on the base. The thickness ofthe porous layer was about 20 μm, and the total thickness of the layeredbody was about 70 μm.

About the resultant layered body Q, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body Q was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 1.5 μm. The porosity of the inside of theporous layer was 69%.

Example 14 Porous Layer Layered Body R

A layered body R wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 13 except that afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP, polyvinyl pyrrolidone and the bisphenol A type epoxy resinwith each other to set the ratio by weight of the polyamideimideresin/NMP/polyvinyl pyrrolidone/the bisphenol A type epoxy resin to15/85/25/20. The thickness of the resultant porous layer was about 20μm, and the total thickness of the layered body was about 70 μm.

About the resultant layered body R, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body R was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 1.5 μm. The porosity of the inside of theporous layer was 65%.

Comparative Example 5 Porous Layer Layered Body S

A layered body S wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 13 except that afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP, and polyvinyl pyrrolidone with each other to set the ratioby weight of the polyamideimide resin/NMP/polyvinyl pyrrolidone to15/85/25 without adding any crosslinking agent to the film-formingmaterial solution. The thickness of the resultant porous layer was about16 μm, and the total thickness of the layered body was about 66 μm.

About the resultant layered body S, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body S was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 1.0 μm. The porosity of the inside of theporous layer was 72%.

Example 15 Porous Layer Layered Body T

A layered body T wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 13 except that asthe water-soluble polymer, polyethylene glycol (average molecularweight: 360 to 440) was used, and a film-forming material solution wasyielded by mixing the polyamideimide resin, NMP, polyethylene glycol,and the bisphenol A type epoxy resin with each other to set the ratio byweight of the polyamideimide resin/NMP/polyethylene glycol/the bisphenolA type epoxy resin to 15/85/25/10. The thickness of the resultant porouslayer was about 7 μm, and the total thickness of the layered body wasabout 57 μm.

About the resultant layered body T, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body T was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 1.0 μm. The porosity of the inside of theporous layer was 39%.

Example 16 Porous Layer Layered Body U

The following were mixed with each other: a polyamideimide resinsolution (trade name: “VYLOMAX N-100H” manufactured by Toyobo Co., Ltd.;solid content concentration: 20% by weight; solvent: NMP; solutionviscosity: 350 dPa·s/25° C.); NMP as a solvent; polyvinyl pyrrolidone(molecular weight: 10000) manufactured by Aldrich Co. as a water-solublepolymer; and a bisphenol A type epoxy resin (trade name: “jER 828”,manufactured by Japan Epoxy Resins Co., Ltd.) as a crosslinking agent.The blend ratio of the polyamideimide resin/NMP/polyvinylpyrrolidone/the bisphenol A type epoxy resin was a ratio by weight of15/85/25/10. In this way, a film-forming material solution was obtained.A polyimide film (trade name: “KAPTON 200H” manufactured by DuPont-Toray Co., Ltd.; thickness: 50 μm) as a base was fixed on a glassplate with a tape. A film applicator was used to cast the materialsolution, the temperature of which was set to 25° C., thereon under acondition that the gap between the film applicator and the base was 51μm. After the casting, the workpiece was rapidly put into a containerhaving a humidity of about 100% and a temperature of 50° C., and thenkept for 4 minutes. Thereafter, the workpiece was immersed in water tocoagulate the cast solution. Next, without peeling the coagulated matterfrom the base, the workpiece was naturally dried at room temperature toyield a layered body U wherein a porous layer was layered on the base.The thickness of the porous layer was about 23 μm, and the totalthickness of the layered body was about 73 μm.

About the resultant layered body U, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body U was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 0.5 μm. The porosity of the inside of theporous layer was 76%. In FIG. 3 is shown an electron microscopicphotograph (power: ×5000) of the porous layer surface, and in FIG. 4 isshown an electron microscopic photograph (power: ×4000) of a crosssection of the layered body.

Example 17 Porous Layer Layered Body V

A layered body V wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 16 except that afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP, polyvinyl pyrrolidone and the bisphenol A type epoxy resinwith each other to set the ratio by weight of the polyamideimideresin/NMP/polyvinyl pyrrolidone/the bisphenol A type epoxy resin to15/85/25/15; and instead of the polyimide film (trade name: “KAPTON200H” manufactured by Du Pont-Toray Co., Ltd.; thickness: 50 μm), apolyimide film (trade name: “KAPTON 200H” manufactured by Du Pont-TorayCo., Ltd.; thickness: 50 μm) subjected to a plasma treatment was used asthe base. The thickness of the resultant porous layer was about 21 μm,and the total thickness of the layered body was about 71 μm.

About the resultant layered body V, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body V was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 0.5 μm. The porosity of the inside of theporous layer was 72%.

Comparative Example 6 Porous Layer Layered Body W

A layered body W wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 16 except that afilm-forming material solution was yielded by mixing the polyamideimideresin, NMP, and polyvinyl pyrrolidone with each other to set the ratioby weight of the polyamideimide resin/NMP/polyvinyl pyrrolidone to15/85/25 without adding any crosslinking agent to the film-formingmaterial solution. The thickness of the resultant porous layer was about20 μm, and the total thickness of the layered body was about 70 μm.

About the resultant layered body W, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body W was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 1.0 μm. The porosity of the inside of theporous layer was 78%.

Comparative Example 7 Porous Layer Layered Body X

A layered body X wherein a porous layer was layered on a base wasyielded by making the same operations as in Example 13 except thatinstead of the polyimide film (trade name: “KAPTON 200H” manufactured byDu Pont-Toray Co., Ltd.; thickness: 50 μm), a PET film (S type;thickness: 100 μm) manufactured by Teijin DuPont Films Japan Ltd. wasused as the base. The thickness of the resultant porous layer was about26 μm, and the total thickness of the layered body was about 76 μm.

About the resultant layered body X, a tape peeling test was made. As aresult, no interfacial peeling was caused between the base and theporous layer. This layered body X was observed through an electronmicroscope. As a result, the porous layer adhered closely to thepolyimide film, and throughout the inside of the porous layer, therewere substantially homogeneous fine pores having interconnection and anaverage pore diameter of about 0.8 μm. The porosity of the inside of theporous layer was 69%.

The respective bases, and the respective porous layer components of theabove-mentioned layered bodies are collectively shown in Table 1. InTable 1, abbreviations are as follows:

-   PI: polyimide,-   PAI: polyamideimide, and-   PET: polyethylene terephthalate.

TABLE 1 Porous-layer-forming solution (ratio by weight) Porous layercomponents Polymer/NMP/crosslinking Base Polymer Crosslinking agentagent/water-soluble polymer Example 1 Layered body A PI PAI YDCN-700-515/85/5/— Example 2 Layered body B PI PAI YDCN-700-5 15/85/10/— Example3 Layered body C PI PAI YDCN-700-5 15/85/15/— Comparative Layered body DPI PAI — 15/85/—/— Example 1 Example 4 Layered body E PI PAI jER 82820/80/10/— Example 5 Layered body F PI PAI jER 834 20/80/10/— Example 6Layered body G PI PAI jER 1001 20/80/10/— Example 7 Layered body H PIPAI jER 1004 20/80/10/— Example 8 Layered body I PI PAI jER 15220/80/10/— Comparative Layered body J PI PAI — 20/80/—/— Example 2Example 9 Layered body K PI PAI jER 828 25/75/5/— Example 10 Layeredbody L PI PAI jER 152 25/75/5/— Comparative Layered body M PI PAI —25/75/—/— Example 3 Example 11 Layered body N PI PI jER 82815.7/84.3/10/— Comparative Layered body O PI PI — 15.7/84.3/—/— Example4 Example 12 Layered body P Copper PAI jER 828 20/80/10/— foil pieceExample 13 Layered body Q PI PAI jER 828 15/85/15/25 Example 14 Layeredbody R PI PAI jER 828 15/85/20/25 Comparative Layered body S PI PAI —15/85/—/25 Example 5 Example 15 Layered body T PI PAI jER 82815/85/10/25 Example 16 Layered body U PI PAI jER 828 15/85/10/25 Example17 Layered body V PI PAI jER 828 15/85/15/25 Comparative Layered body WPI PAI — 15/85/—/25 Example 6 Comparative Layered body X PET PAI jER 82815/85/15/25 Example 7

[Heating Treatment of the Porous Layer Layered Bodies]

The porous film layered body samples A to X yielded in Examples 1 to 17and Comparative Examples 1 to 7, respectively, were each subjected to aheating crosslinking treatment as follows.

Each of the porous film layered body samples A to X was heated on a hotplate under a heating condition (a temperature and a period) shown inTable 2. The heating was conducted in the state that the sample wascovered, from the upper thereof, with a basin made of aluminum andhaving a depth of about 20 mm to heat the whole of the sample evenly.

About each of the porous film layered body samples A to X before andafter the heating crosslinking treatment, in Table 2 are shown resultsof the thickness (μm) of the porous layer, the adhesion evaluating test(cross-cut method) according to JIS K 5600-5-6, and the chemicalresistance evaluating test (the solubility of the porous layer in NMP).In the chemical resistance in Table 2, the word “dissolved” denotes thatthe region of the sample where NMP dropped out was dissolved. Thewording “traces remained” denotes that in the region of the sample whereNMP dropped out, one or more traces thereof were recognized.

In FIG. 5 is shown an electron microscopic photograph (power: ×5000) ofthe porous layer surface of the sample about which the layered body Fyielded in Example 5 was subjected to the heating treatment (at 200° C.for 30 minutes), and in FIG. 6 is shown an electron microscopicphotograph (power: ×2000) of a cross section of the sample.

In FIG. 7 is shown an electron microscopic photograph (power: ×5000) ofthe porous layer surface of the sample about which the layered body Uyielded in Example 16 was subjected to the heating treatment (at 200° C.for 30 minutes), and in FIG. 8 is shown an electron microscopicphotograph (power: ×4000) of a cross section of the sample. When FIGS. 4and 8 are compared with each other, it is observed in FIG. 8 that thefilm thickness of the region of the porous layer became smaller and thefine pores were substantially lost by the heating treatment so that theporous layer was transparentized (into a transparent polymeric layeroriginating from the porous layer).

TABLE 2 Porous layer Adhesion thickness evaluation Chemical resistanceHeating Before After Before After Before condition heating heatingheating heating heating After heating Example 1 Layered 200° C. for 10μm 10 μm 4 0 Dissolved The surface layer was slightly body A 60 minutesinvaded but was not substantially dissolved. Example 2 Layered 200° C.for 11 μm 10 μm 4 0 Dissolved Not dissolved but traces remained body B60 minutes Example 3 Layered 200° C. for 21 μm 16 μm 5 1 Dissolved Notdissolved but traces remained body C 60 minutes Comparative Layered 200°C. for 15 μm 15 μm 5 4 Dissolved Dissolved Example 1 body D 60 minutesExample 4 Layered 200° C. for 23 μm 16 μm 5 0 Dissolved Not dissolvedbut traces remained body E 30 minutes Example 5 Layered 200° C. for 29μm 17 μm 4 0 Dissolved Not dissolved but traces remained body F 30minutes Example 6 Layered 200° C. for 34 μm 23 μm 4 0 Dissolved Notdissolved but traces remained body G 30 minutes Example 7 Layered 200°C. for 30 μm 20 μm 4 2 Dissolved The surface layer was slightly body H30 minutes invaded but was not substantially dissolved. Example 8Layered 200° C. for 31 μm 19 μm 5 0 Dissolved Not dissolved but tracesremained body I 30 minutes Comparative Layered 200° C. for 14 μm 14 μm 54 Dissolved Dissolved Example 2 body J 30 minutes Example 9 Layered 200°C. for 20 μm 18 μm 4 3 Dissolved The surface layer was slightly body K30 minutes invaded but was not substantially dissolved. Example 10Layered 200° C. for 18 μm 17 μm 3 0 Dissolved Not dissolved but tracesremained body L 30 minutes Comparative Layered 200° C. for 20 μm 18 μm 54 Dissolved Dissolved Example 3 body M 30 minutes Example 11 Layered200° C. for 35 μm 29 μm 5 0 Dissolved Not dissolved body N 60 minutesComparative Layered 200° C. for 17 μm 17 μm 5 4 Dissolved Partiallydissolved Example 4 body O 60 minutes Example 12 Layered 200° C. for 32μm 22 μm 5 0 Dissolved Not dissolved body P 60 minutes Example 13Layered 200° C. for 20 μm 7 μm 5 0 Dissolved Not dissolved but tracesremained body Q 30 minutes Example 14 Layered 200° C. for 20 μm 8 μm 5 0Dissolved Not dissolved body R 30 minutes Comparative Layered 200° C.for 16 μm 16 μm 5 4 Dissolved Dissolved Example 5 body S 30 minutesExample 15 Layered 200° C. for 7 μm 6 μm 2 0 Dissolved Not dissolvedbody T 30 minutes Example 16 Layered 200° C. for 23 μm 5 μm 5 0Dissolved Not dissolved body U 30 minutes Example 17 Layered 200° C. for21 μm 6 μm 5 0 Dissolved Not dissolved body V 30 minutes ComparativeLayered 200° C. for 20 μm 20 μm 5 4 Dissolved Dissolved Example 6 body W30 minutes Comparative Layered 180° C. for 26 μm 9 μm 5 4 Dissolved Notdissolved but traces remained Example 7 body X 30 minutes

About most of the respective porous film layered body samples yielded inExamples 1 to 17, the porous layer thickness was decreased by theheating. It appears that their porous layer was shrunken by a thermalcrosslinking reaction. After the heating treatment, the adhesion wasmade remarkably better than before the heating treatment. A remarkableimprovement was made in the film strength of the porous layer (or thepolymeric layer originating from the porous layer), as well as in theadhesion between the base and the porous layer (or the polymeric layeroriginating from the porous layer). These samples were also remarkablyimproved in chemical resistance.

However, about the respective porous film layered body samples yieldedin Comparative Examples 1 to 6, no crosslinking agent was containedtherein; thus, by the heating treatment, no improvement was made in thefilm strength of the porous layer (or the polymeric layer originatingfrom the porous layer), in the adhesion between the base and the porouslayer (or the polymeric layer originating from the porous layer), nor inchemical resistance.

About the porous film layered body sample yielded in Comparative Example7, an improvement was made in chemical resistance by the heatingtreatment since the crosslinking agent was contained therein. However,no improvement was made in the adhesion between the base and the porouslayer (or the polymeric layer originating from the porous layer).

It appears that about each of the polymers having, in the moleculethereof, an imide precursor (amic acid), an imidization reaction alsoadvanced simultaneously by the heating treatment.

Example 18 Formation of an Electroconductive Pattern

In a screen printing manner, a lattice pattern (line width: 20 μm, andpitch: 300 μm) was printed on the porous layer surface of the layeredbody Q [the base/the porous layer=the polyimide film (50 μm)/“thepolyamideimide+jER 828 (20 μm)”] yielded in Example 13 with anelectroconductive ink [silver paste, NANO DOTITE XA9053, manufactured byFujikura Kasei Co., Ltd.] under the following conditions: a printingspeed of 15 mm/sec., a printing pressure of 0.1 MPa, and a clearance of1.5 mm. A screen printing machine used therefor was a machine,LS-150TVA, manufactured by Newlong Seimitsu Kogyo Co., Ltd. A screenplate used therein was a plate manufactured by Mesh Corp.

After the printing, the workpiece was subjected to a heating treatmentat 200° C. for 30 minutes to cure the electroconductive ink, therebyforming wiring. The used ink is of such a type that silver oxide isheated to be reduced into silver. Just after the printing, the printedarea was black; however, after the heating, the printed area showed aluster of metallic silver. The porous layer, which had been yellowishwhite and opaque before the heating, was shrunken in the thicknessdirection when the components (the polymer and the crosslinking agent)of the layer were thermally crosslinked. Thus, the thickness was reducedfrom about 20 μm to about 7 μm, and the porous layer turned into aground glass form to be in a slightly see-through state that one sidethereof was slightly viewable from the other side.

In this way, an electromagnetic wave shield film was produced. Theresultant electromagnetic wave shield film was observed through anelectron microscope. As a result, a lattice-form electroconductivepattern was formed which had a line width of 20 μm and a pitch of 300μm. In FIG. 9 is shown an electron microscopic photograph (power: ×100)of the electroconductive pattern.

Example 19 Formation of an Electroconductive Pattern

The layered body Q yielded in Example 13 was heated on a hot plate undera heating condition of 200° C. for 30 minutes to cause a reaction(thermal crosslinking) between the polymer having a crosslinkablefunctional group and the crosslinking agent. The heating was conductedin the state that the sample was covered, from the upper thereof, with abasin made of aluminum and having a depth of about 20 mm to heat thewhole of the sample evenly. The porous layer, which had been yellowishwhite and opaque before the heating, was shrunken in the thicknessdirection when the components (the polymer and the crosslinking agent)of the layer were thermally crosslinked. Thus, the thickness was reducedfrom about 20 μm to about 7 and the porous layer turned into a groundglass form to be in a slightly see-through state that one side thereofwas slightly viewable from the other side.

Under the same conditions as in Example 18, screen printing was appliedonto the porous layer surface with an electroconductive ink [silverpaste, NANO DOTITE XA9053, manufactured by Fujikura Kasei Co., Ltd.].After the printing, the workpiece was subjected to a heating treatmentat 200° C. for 30 minutes to cure the electroconductive ink, therebyforming wiring. Just after the printing, the printed area was black;however, after the heating, the printed area showed a luster of metallicsilver.

In this way, an electromagnetic wave shield film was produced. Theresultant electromagnetic wave shield film was observed through anelectron microscope. As a result, a lattice-form electroconductivepattern was formed which had a line width of 20 μm and a pitch of 300μm. In FIG. 10 is shown an electron microscopic photograph (power: ×100)of the electroconductive pattern.

Example 20 Formation of an Electroconductive Pattern

The layered body Q yielded in Example 13 was heated on a hot plate undera heating condition of 140° C. for 5 minutes to cause a reaction(thermal crosslinking) partially between the polymer having acrosslinkable functional group and the crosslinking agent. In this way,the layered body was made into a B stage (semi-cured state). The heatingwas conducted in the state that the sample was covered, from the upperthereof, with a basin made of aluminum and having a depth of about 20 mmto heat the whole of the sample evenly. The porous layer, which had beenyellowish white and opaque before the heating, was slightly shrunken inthe thickness direction when the components (the polymer and thecrosslinking agent) of the layer were partially thermally crosslinked.Thus, the thickness was reduced from about 20 μm to about 14 μm.However, the external appearance hardly changed to be kept in theyellowish white and opaque state.

Under the same conditions as in Example 18, screen printing was appliedonto the porous layer surface with an electroconductive ink [silverpaste, NANO DOTITE XA9053, manufactured by Fujikura Kasei Co., Ltd.].After the printing, the workpiece was subjected to a heating treatmentat 200° C. for 30 minutes to cure the electroconductive ink, therebyforming wiring. Just after the printing, the printed area was black;however, after the heating, the printed area showed a luster of metallicsilver. The porous layer, which had been yellowish white and opaqueafter the printing and before the heating, was shrunken in the thicknessdirection when the components (the polymer and the crosslinking agent)of the layer were thermally crosslinked. Thus, the thickness was reducedto about 7 μm, and the porous layer turned into a ground glass form tobe in a slightly see-through state that one side thereof was slightlyviewable from the other side.

In this way, an electromagnetic wave shield film was produced. Theresultant electromagnetic wave shield film was observed through anelectron microscope. As a result, a lattice-form electroconductivepattern was formed which had a line width of 20 μm and a pitch of 300μm. In FIG. 11 is shown an electron microscopic photograph (power: ×100)of the electroconductive pattern.

Example 21 Formation of an Electroconductive Pattern

In a screen printing manner, a wiring pattern in a 200-μm line and spaceform (L/S=200 μm/200 μm) was printed on the layered body F [the base/theporous layer=the polyimide film (50 μm)/“the polyamideimide+jER 834 (29μm)”] yielded in Example 5 with an electroconductive ink [silver paste,NANO DOTITE XA9053, manufactured by Fujikura Kasei Co., Ltd.] under thefollowing conditions: a printing speed of 30 mm/sec., and a printingpressure of 0.1 MPa. A screen printing machine used therefor was amachine, LS-25TVA, manufactured by Newlong Seimitsu Kogyo Co., Ltd.After the printing, the workpiece was kept at 200° C. for 30 minutes tocure the electroconductive ink, thereby forming wiring. The used ink isof such a type that silver oxide is heated to be reduced into silver.Just after the printing, the printed area was black; however, after theheating, the printed area showed a luster of metallic silver. Theresultant was observed through an electron microscope. As a result, awiring pattern wherein L/S was 200 μm/200 μm was formed.

Example 22 Formation of an Electroconductive Pattern

The layered body F yielded in Example 5 was heated on a hot plate undera heating condition of 200° C. for 30 minutes to cause a reaction(thermal crosslinking) between the polymer having a crosslinkablefunctional group and the crosslinking agent. The heating was conductedin the state that the sample was covered, from the upper thereof, with abasin made of aluminum and having a depth of about 20 mm to heat thewhole of the sample evenly. The porous layer, which had been yellowishwhite and opaque before the heating, was slightly shrunken in thethickness direction when the components (the polymer and thecrosslinking agent) of the layer were thermally crosslinked. Thus, thethickness was reduced from about 29 μm to about 17 μm. However, theexternal appearance hardly changed to be kept in the yellowish white andopaque state.

Under the same conditions as in Example 21, screen printing was appliedonto the porous layer surface with an electroconductive ink [silverpaste, NANO DOTITE XA9053, manufactured by Fujikura Kasei Co., Ltd.].After the printing, the workpiece was kept at 200° C. for 30 minutes tocure the electroconductive ink, thereby forming wiring. Just after theprinting, the printed area was black; however, after the heating, theprinted area showed a luster of metallic silver. The resultant wasobserved through an electron microscope. As a result, a wiring patternwherein L/S was 200 μm/200 μm was formed.

Example 23 Formation of an Electroconductive Pattern

The same operations as in Example 21 were made except that as thelayered body, use was made of the layered body I [the base/the porouslayer=the polyimide film (50 μm)/“the polyamideimide+jER 152 (31 μm)”]yielded in Example 8, so as to print a wiring pattern wherein L/S was tobe 200 μm/200 μm in a screen printing manner. In this way, a wiringboard was yielded. The resultant wiring board was observed through anelectron microscope. As a result, the formed wiring pattern was a wiringpattern wherein L/S was 200 μm/200 μm.

Example 24 Formation of an Electroconductive Pattern

In a screen printing manner, a lattice pattern (line width: 20 μm, andpitch: 300 μm) was printed on the porous layer surface of the layeredbody U [the base/the porous layer=the polyimide film (50 μm)/“thepolyamideimide resin+jER 828 (23 μm)”] yielded in Example 16 with anelectroconductive ink [silver paste, NANO DOTITE XA9053, manufactured byFujikura Kasei Co., Ltd.] under the following conditions: a printingspeed of 15 mm/sec., a printing pressure of 0.1 MPa, and a clearance of1.5 mm. A screen printing machine used therefor was a machine,LS-150TVA, manufactured by Newlong Seimitsu Kogyo Co., Ltd. A screenplate used therein was a plate manufactured by Mesh Corp. After theprinting, the workpiece was subjected to a heating treatment on a hotplate, the temperature of which was set to 200° C., for 30 minutes tocure the electroconductive ink, thereby forming wiring. The heating wasconducted in the state that the sample was covered, from the upperthereof, with a basin made of aluminum and having a depth of about 20 mmto heat the whole of the sample evenly. The used ink is of such a typethat silver oxide is heated to be reduced into silver. Just after theprinting, the printed area was black, but after the heating, the printedarea showed a luster of metallic silver. However, the film contactregion was kept black. The porous layer, which had been yellowish whitebefore the heating, was transparent. In this way, an electromagneticwave shield film was produced. The resultant electromagnetic wave shieldfilm was observed through an electron microscope. As a result, anelectroconductive pattern was formed which was in the form of a latticehaving a line width of 20 μm and a pitch of 300 μm.

By the heating treatment at 200° C. for 30 minutes after the printing,the porous layer composition was softened so that the fine poressubstantially disappeared, and simultaneously a crosslinking reactionwas caused. The situation at this time was equivalent to that accordingto the electron microscopic photograph (power: ×4000) (FIG. 8) of thecross section of the sample obtained by subjecting the layered body Uyielded in Example 16 to the heating treatment (at 200° C. for 30minutes).

The polyimide film (trade name: “KAPTON 200H” manufactured by DuPont-Toray Co., Ltd.; thickness: 50 μm) had a total light transmittance(Ts) of 41.0%, the layered body U had a total light transmittance (Tsp)of 8.1%, and in the transparentized layered body, the region where nowiring was formed had a total light transmittance (Tst) of 38.1%.

Accordingly, after the heating treatment, the transparent layeroriginating from the porous layer had a transparency (T) of 2.9%. Theporous layer not subjected to the heating treatment had an opacity (P)of 32.9%.

The above-mentioned total light transmittances were each measured asfollows:

The total light transmittance (%) was measured by use of a haze meter,NDH-5000W, manufactured by Nippon Denshoku Industries Co., Ltd.according to JIS K7136.

First, the total light transmittance (Ts) of the used base itself wasmeasured.

The total light transmittance (Tsp) of the porous layer layered body(the base+the porous layer) not subjected to the heating treatment wasthen measured.

Finally, the total light transmittance (Tst) of the no-wiring-formedregion of the layered body (the base+the transparent layer)transparentized by the heating treatment was measured.

The transparency (T) of the transparent layer=|the total lighttransmittance (Ts) of the base itself−the total light transmittance(Tst) of the layered body (the base+the transparent layer)|

The opacity (P) of the porous layer=|the total light transmittance (Ts)of the base itself−the total light transmittance (Tsp) of the porouslayer layered body (the base+the porous layer)|

1. A layered body, comprising a base, and a porous layer on at least one surface of the base, wherein the base is a resin film made of at least one resin material selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyetherimide resins, or is a metal foil piece, the porous layer is made of a composition containing at least one polymer selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyetherimide resins as a main component, and a crosslinking agent, and the porous layer has fine pores having an average pore diameter of 0.01 to 10 μm, and a porosity of 30 to 85%.
 2. The layered body according to claim 1, wherein the crosslinking agent is at least one selected from the group consisting of compounds each having two or more epoxy groups, polyisocyanate compounds, and silane coupling agents.
 3. The layered body according to claim 1, wherein the porous layer has a thickness of 0.1 to 100 μm.
 4. The layered body according to claim 1, wherein the porous layer is a layer formed by casting, on the base, a solution of a porous-layer-forming material containing the polymer, which is to constitute the porous layer, and the crosslinking agent into a film form, subsequently immersing this workpiece into a coagulating liquid, and next drying the workpiece.
 5. The layered body according to claim 1, wherein the crosslinking agent comprised in the porous layer is in an unreacted state.
 6. The layered body according to claim 1, wherein the porous layer is a layer having a crosslinked structure formed with the crosslinking agent.
 7. A process for producing the layered body recited in claim 1, comprising: casting, on the base, a solution of a porous-layer-forming material containing the polymer, which is to constitute the porous layer, and the crosslinking agent into a film form; subsequently immersing this workpiece into a coagulating liquid; and next drying the workpiece.
 8. The layered body-producing process according to claim 7, wherein after the solution of the porous-layer-forming material is casted into the film form on the base, the resultant workpiece is kept in an atmosphere having a relative humidity of 70 to 100% and a temperature of 15 to 100° C. for 0.2 to 15 minutes, and then this workpiece is immersed in the coagulating liquid.
 9. A functional laminate, comprising the layered body recited in claim 1, and comprising, over the surface of the porous layer of the layered body or a polymeric layer originating from the porous layer, a functional layer selected from the group consisting of an electroconductor layer, a dielectric layer, a semiconductor layer, an electric insulator layer, and a resistor layer, wherein the porous layer or the polymeric layer originating from the porous layer has a crosslinked structure formed with the crosslinking agent.
 10. The functional laminate according to claim 9, wherein the functional layer is patterned.
 11. A process for producing a functional laminate comprising the layered body recited in claim 1, and comprising, over the surface of the porous layer of the layered body or a polymeric layer originating from the porous layer, a functional layer selected from the group consisting of an electroconductor layer, a dielectric layer, a semiconductor layer, an electric insulator layer, and a resistor layer, comprising: forming a layer selected from the group consisting of the electroconductor layer, the dielectric layer, the semiconductor layer, the electric insulator layer and the resistor layer, and a precursor layer thereof over the surface of the porous layer of the layered body recited in any one of claims 1 to 4; and subjecting the resultant workpiece to a heating treatment and/or an active energy ray radiating treatment, thereby forming a crosslinked structure with the crosslinking agent in the porous layer.
 12. The functional laminate according to claim 11, wherein the functional layer is patterned.
 13. The layered body according to claim 2, wherein the porous layer has a thickness of 0.1 to 100 μm.
 14. The layered body according to claim 2, wherein the porous layer is a layer formed by casting, on the base, a solution of a porous-layer-forming material containing the polymer, which is to constitute the porous layer, and the crosslinking agent into a film form, subsequently immersing this workpiece into a coagulating liquid, and next drying the workpiece.
 15. The layered body according to claim 3, wherein the porous layer is a layer formed by casting, on the base, a solution of a porous-layer-forming material containing the polymer, which is to constitute the porous layer, and the crosslinking agent into a film form, subsequently immersing this workpiece into a coagulating liquid, and next drying the workpiece.
 16. The layered body according to claim 2, wherein the crosslinking agent comprised in the porous layer is in an unreacted state.
 17. The layered body according to claim 3, wherein the crosslinking agent comprised in the porous layer is in an unreacted state.
 18. The layered body according to claim 4, wherein the crosslinking agent comprised in the porous layer is in an unreacted state.
 19. The layered body according to claim 2, wherein the porous layer is a layer having a crosslinked structure formed with the crosslinking agent.
 20. The layered body according to claim 3, wherein the porous layer is a layer having a crosslinked structure formed with the crosslinking agent. 